A rash is an area of irritated or swollen skin. Many rashes are itchy, red, painful, and irritated. Some rashes can also lead to blisters or patches of raw skin. Rashes are a symptom of many different medical problems. Other causes include irritating substances and allergies. Certain genes can make people more likely to get rashes.

Contact dermatitis is a common type of rash. It causes redness, itching, and sometimes small bumps. You get the rash where you have touched an irritant, such as a chemical, or something you are allergic to, like poison ivy.

Some rashes develop right away. Others form over several days. Although most rashes clear up fairly quickly, others are long-lasting and need long-term treatment.

Because rashes can be caused by many different things, it's important to figure out what kind you have before you treat it. If it is a bad rash, if it does not go away, or if you have other symptoms, you should see your health care provider. Treatments may include moisturizers, lotions, baths, cortisone creams that relieve swelling, and antihistamines, which relieve itching.

Skin rash means abnormal areas on the skin that may appear as discolored bumps or flat spots or areas, or blisters or bumps containing fluid or pus that are intact or crusted over. “Rash” includes insect bites or parasite lesions.

• Color: ranges from light-colored to red or pink, purple, or black, but can also be the same color as the person’s skin tone.
• Texture: can be flat, raised, blister-like, or crusted. In some diseases, such as chickenpox, areas with more than one of these characteristics can be found at the same time.
• Select the most appropriate description of the rash’s appearance:
  • Maculopapular: A red rash with both flat red areas (macules) and small bumps (papules) that may run together.
  • Vesicular/Pustular: Small bumps filled with fluid that can be clear or cloudy (vesicles) or filled with a thick, opaque fluid (pustules).
  • Purpuric/Petechial: Red or purple discolorations caused by bleeding under the skin or mucous membranes; they do not blanch or fade with pressure. Petechial lesions appear as small, reddish freckles, while purpuric lesions cover larger areas.
  • Scabbed: Lesions that are crusted over.
  • Other: Enter a short description of the rash appearance if the other options do not apply.
• Pattern: can be disconnected (discrete) or run together (confluent).
• Location: may include one area of the body, such as the face, or more than one area.

Fever plus rash may indicate communicable diseases such as chickenpox, measles, or rubella (German measles).

You’ve probably had a rash at some point or another, whether from poison ivy or the chickenpox or something more unusual. Why does your skin break out in red blotches like that? More important, is there anything you can do about it?

We often think of the skin as a barrier—it keeps the insides of our bodies in, and it keeps the outside world out. But our skin is also filled with special cells of the immune system. These cells protect the skin and body against viruses, bacteria and other threats. Whenever these cells detect a suspicious substance, they begin a chain reaction in the skin that leads to inflammation. The medical name for this reaction is dermatitis. But it’s more commonly known as a rash.

There are many different types of dermatitis, and each has a distinct set of treatments. Sometimes the skin’s immune cells react to something that directly touches the skin. Other times, the immune system flares in the skin because of a whole-body infection or illness.

The symptoms of these different types of rashes often overlap. “Itching is a common symptom for all these problems,” says Dr. Stephen I. Katz, director of NIH’s National Institute of Arthritis and Musculoskeletal and Skin Diseases. Many rashes are red, painful, and irritated. Some types of rash can also lead to blisters or patches of raw skin. While most rashes clear up fairly quickly, others are long lasting and need to be cared for over long periods of time.

Eczema, or atopic dermatitis, is a dry, red, itchy rash that affects up to 1 in 5 infants and young children. It often improves over time, although it can last into adulthood or start later in life. In this condition, the water-tight barrier between skin cells gets weak, which lets moisture out and other things in. That’s why people with atopic dermatitis have to moisturize their skin, and they’re more susceptible to skin infections.

Researchers have recently identified specific genes that are involved in maintaining the skin barrier. People with certain versions of these genes are more likely to get atopic dermatitis.

“The skin is the outermost sentinel for fighting off bacteria and noxious agents,” says Katz. “If the barrier is broken somehow, you can become more allergic to things.”

A skin allergy, or allergic contact dermatitis, produces a red, itchy rash that sometimes comes with small blisters or bumps. The rash arises when the skin comes in contact with an allergen, a usually harmless substance that the immune system attacks. Allergens trigger allergic reactions. Allergens can come from certain soaps, creams and even pets.

Your immune system might not react the first time you encounter an allergen. But over time, your immune system can become sensitive to the substance. As a result, your next contact may lead to inflammation and an allergic rash.

“The most common form of dermatitis that is seen anywhere is an allergic contact dermatitis to nickel,” says Katz. “Why? Because of ear piercing.” Many inexpensive earrings are made of nickel, and over time, wearing nickel earrings can cause an allergic reaction to the metal.

Other common causes of allergic dermatitis are poison oak and poison ivy. The stems and leaves of these plants produce a chemical that’s likely to cause allergies. If you touch one of them, wash your skin as soon as possible. The chemical can also remain in clothing for a long time, so it’s important to wash any clothes or shoes—or even pets—that come into contact with these plants.

Mild cases of allergic contact dermatitis usually disappear after a few days or weeks. But if the rash persists, is extremely uncomfortable or occurs on the face, it’s important to see a physician. A doctor can prescribe medications that will tone down the immune reaction in the skin. This eases swelling and itching and will protect your eyes and face.

The immune cells of the skin can also produce rashes when they react to invading germs—like bacteria, fungi and viruses. Bacterial and viral infections within your body can cause your skin to break out in spots as well. The chickenpox virus, for example, can cause itchy spots in children. Years later, in older adults, the same virus may reappear as shingles, bringing a painful rash and high fever. Vaccines can prevent several rash-causing diseases, including chickenpox, shingles and measles.

Certain drugs, including antibiotics like amoxicillin, may also cause itchy skin rashes. If you’re allergic to a drug, a rash can be the first sign of a serious reaction. As with other allergies, a reaction to a drug may not occur the first time you take it. It could show up after several uses. Not all drug rashes are due to an allergy, however. If you break out in itchy spots after starting a new drug prescription, contact your doctor right away.

While most rashes get better with time, some can last a lifetime. Psoriasis, a condition where skin cells build up into thick red patches, tends to run in families. “It’s a complex genetic disease, in that there’s not one gene that causes psoriasis but many,” says Katz. Even though none of these genes alone has a great effect on the disease, knowing which genes are involved can help researchers design potential new treatments. Other long-term diseases that can produce rashes include autoimmune diseases, such as lupus, and some forms of cancer.

If you notice an itchy or painful rash on your skin, think twice before going to the drugstore and getting some cream if you don’t know the cause. “The creams that you buy can produce problems that make your original problem even worse,” Katz says. Because rashes can be caused by many different things—bacteria, viruses, drugs, allergies, genetic disorders, and even light—it’s important to figure out what kind of dermatitis you have.

“If you have any significant rash, you should see a dermatologist,” says Katz. A dermatologist, or skin doctor, is specially trained to figure out what’s causing a rash and help you get the right treatment.

Your skin is your protection. It’s not just the covering that keeps your body in; it’s also your first line of defense against germs and chemicals. Take care of your skin so your skin can take care of you.

Call Your Doctor If …

• Your rash is so uncomfortable or painful it interferes with daily activities or sleep.
• The rash is on your face.
• Your rash looks worrisome or seems infected.
• You break out in a rash after taking a new medication.
• Your rash lasts for several days.

Eczema is an allergic reaction that manifests as dry, itchy patches of skin that resemble rashes (Figure). It may be accompanied by swelling of the skin, flaking, and in severe cases, bleeding. Many who suffer from eczema have antibodies against dust mites in their blood, but the link between eczema and allergy to dust mites has not been proven. Symptoms are usually managed with moisturizers, corticosteroid creams, and immunosuppressants.

Eczema Eczema is a common skin disorder that presents as a red, flaky rash. (credit: “Jambula”/Wikimedia Commons)

The damage and pathology of systemic lupus erythematosus (SLE) is caused by type III hypersensitivity reactions. Autoantibodies produced in SLE are directed against nuclear and cytoplasmic proteins. Anti-nuclear antibodies (ANAs) are present in more than 95% of patients with SLE, with additional autoantibodies including anti-double–stranded DNA (ds-DNA) and anti-Sm antibodies (antibodies to small nuclear ribonucleoprotein). Anti-ds-DNA and anti-Sm antibodies are unique to patients with SLE; thus, their presence is included in the classification criteria of SLE. Cellular interaction with autoantibodies leads to nuclear and cellular destruction, with components released after cell death leading to the formation of immune complexes.

Because autoantibodies in SLE can target a wide variety of cells, symptoms of SLE can occur in many body locations. However, the most common symptoms include fatigue, fever with no other cause, hair loss, and a sunlight-sensitive "butterfly" or wolf-mask (lupus) rash that is found in about 50% of people with SLE (Figure). The rash is most often seen over the cheeks and bridge of the nose, but can be widespread. Other symptoms may appear depending on affected areas. The joints may be affected, leading to arthritis of the fingers, hands, wrists, and knees. Effects on the brain and nervous system can lead to headaches, numbness, tingling, seizures, vision problems, and personality changes. There may also be abdominal pain, nausea, vomiting, arrhythmias, shortness of breath, and blood in the sputum. Effects on the skin can lead to additional areas of skin lesions, and vasoconstriction can cause color changes in the fingers when they are cold (Raynaud phenomenon). Effects on the kidneys can lead to edema in the legs and weight gain. A diagnosis of SLE depends on identification of four of 11 of the most common symptoms and confirmed production of an array of autoantibodies unique to SLE. A positive test for ANAs alone is not diagnostic.

(a) Systemic lupus erythematosus is characterized by autoimmunity to the individual’s own DNA and/or proteins. (b) This patient is presenting with a butterfly rash, one of the characteristic signs of lupus. (credit a: modification of work by Mikael Häggström; credit b: modification of work by Shrestha D, Dhakal AK, Shiva RK, Shakya A, Shah SC, Shakya H)

While the microbiota of the skin can play a protective role, it can also cause harm in certain cases. Often, an opportunistic pathogen residing in the skin microbiota of one individual may be transmitted to another individual more susceptible to an infection. For example, methicillin-resistant Staphylococcus aureus (MRSA) can often take up residence in the nares of health care workers and hospital patients; though harmless on intact, healthy skin, MRSA can cause infections if introduced into other parts of the body, as might occur during surgery or via a post-surgical incision or wound. This is one reason why clean surgical sites are so important.

Injury or damage to the skin can allow microbes to enter deeper tissues, where nutrients are more abundant and the environment is more conducive to bacterial growth. Wound infections are common after a puncture or laceration that damages the physical barrier of the skin. Microbes may infect structures in the dermis, such as hair follicles and glands, causing a localized infection, or they may reach the bloodstream, which can lead to a systemic infection.

In some cases, infectious microbes can cause a variety of rashes or lesions that differ in their physical characteristics. These rashes can be the result of inflammation reactions or direct responses to toxins produced by the microbes. The table below lists some of the medical terminology used to describe skin lesions and rashes based on their characteristics; the images below illustrate some of the various types of skin lesions. It is important to note that many different diseases can lead to skin conditions of very similar appearance; thus the terms used in the table are generally not exclusive to a particular type of infection or disease.

Table

(a) Acne is a bacterial infection of the skin that manifests as a rash of inflamed hair follicles (folliculitis). The large whitehead near the center of the cheek is an infected hair follicle that has become purulent (or suppurative), leading to the formation of a furuncle. (b) An abscess is a pus-filled lesion. (credit b: modification of work by Bruce Blaus)

Numerous causes can lead to skin lesions of various types, some of which are very similar in appearance. (credit: modification of work by Bruce Blaus)

Candida albicans and other yeasts in the genus Candida can cause skin infections referred to as cutaneous candidiasis. Candida spp. are sometimes responsible for intertrigo, a general term for a rash that occurs in a skin fold, or other localized rashes on the skin. Candida can also infect the nails, causing them to become yellow and harden (Figure).

(a) This red, itchy rash is the result of cutaneous candidiasis, an opportunistic infection of the skin caused by the yeast Candida albicans. (b) Fungal infections of the nail (tinea unguium) can be caused by dermatophytes or Candida spp. The nail becomes yellow, brittle, and prone to breaking. This condition is relatively common among adults. (c) C. albicans growing on Sabouraud dextrose agar. (credit a: modification of work by U.S. Department of Veterans Affairs; credit c: modification of work by Centers for Disease Control and Prevention)

Candidiasis of the skin and nails is diagnosed through clinical observation and through culture, Gram stain, and KOH wet mounts. Susceptibility testing for anti-fungal agents can also be done. Cutaneous candidiasis can be treated with topical or systemic azole antifungal medications. Because candidiasis can become invasive, patients suffering from HIV/AIDS, cancer, or other conditions that compromise the immune system may benefit from preventive treatment. Azoles, such as clotrimazole, econazole, fluconazole, ketoconazole, and miconazole; nystatin; terbinafine; and naftifine may be used for treatment. Long-term treatment with medications such as itraconazole or ketoconazole may be used for chronic infections. Repeat infections often occur, but this risk can be reduced by carefully following treatment recommendations, avoiding excessive moisture, maintaining good health, practicing good hygiene, and having appropriate clothing (including footwear).

Common streptococcal conditions of the skin include cellulitis, erysipelas, and erythema nodosum. An infection that develops in the dermis or hypodermis can cause cellulitis, which presents as a reddened area of the skin that is warm to the touch and painful. The causative agent is often S. pyogenes, which may breach the epidermis through a cut or abrasion, although cellulitis may also be caused by staphylococci. S. pyogenes can also cause erysipelas, a condition that presents as a large, intensely inflamed patch of skin involving the dermis (often on the legs or face). These infections can be suppurative, which results in a bullous form of erysipelas. Streptococcal and other pathogens may also cause a condition called erythema nodosum, characterized by inflammation in the subcutaneous fat cells of the hypodermis. It sometimes results from a streptococcal infection, though other pathogens can also cause the condition. It is not suppurative, but leads to red nodules on the skin, most frequently on the shins (Figure).

In general, streptococcal infections are best treated through identification of the specific pathogen followed by treatment based upon that particular pathogen’s susceptibility to different antibiotics. Many immunological tests, including agglutination reactions and ELISAs, can be used to detect streptococci. Penicillin is commonly prescribed for treatment of cellulitis and erysipelas because resistance is not widespread in streptococci at this time. In most patients, erythema nodosum is self-limiting and is not treated with antimicrobial drugs. Recommended treatments may include nonsteroidal anti-inflammatory drugs (NSAIDs), cool wet compresses, elevation, and bed rest.

S. pyogenes can cause a variety of skin conditions once it breaches the skin barrier through a cut or wound. (a) Cellulitis presents as a painful, red rash. (b) Erysipelas presents as a raised rash, usually with clear borders. (c) Erythema nodosum is characterized by red lumps or nodules, typically on the lower legs. (credit a: modification of work by “Bassukas ID, Gaitanis G, Zioga A, Boboyianni C, Stergiopoulou C; credit b: modification of work by Centers for Disease Control and Prevention; credit c: modification of work by Dean C, Crow WT)

If contaminated water stays on someone’s skin for a long time, it can cause a rash known as “hot tub rash” (Pseudomonas folliculitis). Hot tub rash is caused by the germ Pseudomonas aeruginosa. This germ is commonly found in the environment (for example, in water or soil).

Hot tub rash usually appears a few days after you sat in a poorly maintained hot tub/spa, but it can also appear a few days after you swam in a lake or poorly maintained pool.

Signs and symptoms

Hot tub rash can affect people of all ages. It is often worse in areas where a swimsuit held water up against the skin. Symptoms include:

• Itchy, red, and bumpy rash
• Pus-filled blisters around hair follicles

Mild rashes clear up in a few days without medical treatment. Check with your healthcare provider if a rash gets worse or if you get it more than once.

Preventing hot tub rash

To reduce the risk of hot tub rash:

• Remove your swimsuit and shower with soap after getting out of the water, especially hot tubs/spas.
• Wash your swimsuit after using it.
• Use test strips to check the water in the hot tub/spa or pool yourself for adequate disinfectant level and pH.

CDC recommends the following disinfectant and pH levels:

• Disinfectant

• • Hot Tubs/Spas: free chlorine 3–10 parts per million (ppm or mg/L) or bromine 4–8 ppm
  • Pools: free chlorine 1–10 ppm or bromine 3–8 ppm

• pH

• • Both hot tubs/spas and pools: pH 7.2–8

If chlorine or bromine level or pH is not within the correct range, tell the hot tub/spa operator or owner immediately.

If you spend time outdoors, chances are you have been bothered by poison ivy, poison oak or poison sumac at some point. Most people are sensitive to the plants' oily sap. The sap is in the root, stems, leaves and fruit of these plants. If it gets on your skin, it causes a blistering skin rash. The rash can range from mild to severe, depending on how much sap gets on your skin and how sensitive you are to it. Problems can also happen if the plants are burned. Airborne sap-coated soot can get into the eyes, nose, throat and respiratory system.

The best way to avoid the rash is to learn what the plants look like and stay away from them. If you come into contact with the plants, wash your skin and clothing right away. If you develop a rash, ask your pharmacist about over-the-counter medicines. For severe rashes, see your doctor.

You’ve broken out in a red, itchy rash. You’re likely wondering where it came from—and, most importantly, how to make it go away.

Unfortunately, your mystery rash could have many causes. Maybe you switched to a new detergent or accidentally brushed against poison ivy. Maybe it came from a virus or fungus. It can be hard to pinpoint the cause.

Red, uncomfortable skin rashes are called dermatitis. “When we use the term dermatitis, all we really mean is skin inflammation,” says Dr. Brian Kim, a dermatologist at Washington University in St. Louis.

Our skin is a barrier, serving as the first line of defense against the outside world. It is filled with immune cells. These cells actively fight against viruses, bacteria, and other invaders. If a foreign substance is detected, immune cells start a chain reaction to neutralize the threat. This, in turn, causes inflammation.

Eczema

Many people are familiar with atopic dermatitis—the red, itchy rash commonly called eczema. “It affects up to 30% of people, particularly in childhood, and it tends to run in families,” explains Dr. Heidi Kong, a dermatologist at NIH. While some children may outgrow eczema, others will have the disease for life.

The cause of eczema is unknown. But skin microbes—bacteria, fungi, and viruses—may play a role. Kong is working to understand how the millions of microbes that live on your skin may contribute to eczema. Kong and her team have shown that certain types of bacteria are more commonly found on people with eczema. When applied to the skin of mice, these bacteria cause an immune response in the skin.

“We’re trying to understand the bacteria on a deeper level,” says Kong. “We see that they are associated with flares.” Flares are periods when eczema gets worse.

Treatment using bacteria normally found on healthy skin may help. In a small preliminary study, children and adults with eczema improved after using a spray that contained a specific kind of healthy bacteria. Research like this may one day lead to new treatments.

Scientists are also interested in understanding whether eczema can be prevented before it starts.

“I tell my patients that you were probably programmed from birth to be at risk for developing atopic dermatitis,” says Dr. Eric Simpson, a dermatologist at Oregon Health & Science University. Scientists estimate that the risk for eczema may be up to 60–70% genetic. But environmental causes also play a role.

What if a simple act, like moisturizing daily, could keep children from developing the disease? Doctors often prescribe moisturizing creams for people with eczema. These creams help to stop itching and restore the skin. Studies have shown that using moisturizers, sometimes called emollients, can prevent eczema flares.

In Simpson’s new study, parents will moisturize their baby’s entire body each day using one of several emollients. “Our idea was to repair the skin barrier that’s dysfunctional as early in life as you can,” says Simpson.

Over several years, the team will be able to see whether emollient treatment helped prevent eczema. They are also looking at whether regular moisturizing could impact allergies and asthma, which are common for children with eczema.

How do you choose a moisturizing product if you have eczema? “It’s a bit of trial and error,” Kong says. While some people prefer petroleum jelly-based products, other people find they have better results with cream-based lotions.

“But because of the tendency for a lot of these patients to have sensitive skin, we do recommend they avoid products that have a lot of fragrances or preservatives,” she says.

Other Rashes

Not all rashes are mysterious. Some have a very clear cause. If your skin touches something you’re allergic to, it’s bound to get red and itchy. Common triggers include fragrances in soaps, lotions, and cosmetics. Some people are sensitive to nickel, which is often found in jewelry.

Your doctor may recommend a “patch test.” Small amounts of different substances are applied to your skin to see if you have a reaction.

“People are very familiar with allergic contact dermatitis by way of poison ivy,” Kim says. “But there are many, many environmental allergens that can cause contact dermatitis.” Luckily, hydrocortisone cream may be all you need if the rash only covers a small area.

Psoriasis is another common form of dermatitis. It causes thick, red, scaly skin on the elbows, knees, scalp, and other parts of the body. It’s caused by an overactive immune system. Skin ointments and medications that quiet the immune system can help. A doctor may also prescribe light therapy, where the skin is regularly exposed to ultraviolet light.

Rashes can also be triggered by bacterial and viral infections. And certain drugs may cause an itchy skin rash if you’re allergic.

“That’s a few of probably hundreds of rashes you can get,” Kim says. But common to all of them? “A five-year-old child could tell you that whenever something’s rashy, it itches. Itch is probably the most common symptom in the field of dermatology.”

Itch Relief

For a long time, people questioned whether itch was even its own unique sensation. They thought it might be a mild form of pain. But scientists have discovered that itch has its own pathway in the brain.

That was the starting point for developing new treatments for chronic itch. Now researchers are focusing on finding drugs to help fight itch.

If you’re a little itchy, it’s okay to start with over-the-counter creams. Moisturizers and creams work well for dry, itchy skin. Mentholated moisturizers can cool the skin and provide relief. But some perfumes or dyes added to skin lotions may make things worse. For more tips on soothing a mild rash, see the “Wise Choices” box.

If you have a severe itch that’s been going on for a long time, you should see a doctor. For these types of severe itch, Kim says, trying to use over-the-counter treatments is “like trying to put out a fire with a garden hose.”

For an itchy rash, it’s important to understand the cause. Call your doctor if your rash is so uncomfortable that it interferes with your sleep or daily activities. You should also seek medical help if you break out in a rash after taking a new medication.

An itchy rash can be trying, but with help, you can calm your skin and feel better.

Mild Rash Relief

These tips may help soothe some rashes:

• Use moisturizer to calm your skin.
• Consider using over-the-counter medications like hydrocortisone if the rash covers a small area.
• Take a lukewarm bath.
• Avoid rubbing and scratching.
• Wear cotton clothing so the rash doesn’t worsen.
• Get medical help if your itch is severe or has been going on for a long time.

Have you ever had a skin rash that did not respond to over-the-counter creams, or a mole that you were concerned about? Dermatologists help patients with these types of problems and more, on a daily basis. Dermatologists are medical doctors who specialize in diagnosing and treating skin disorders. Like all medical doctors, dermatologists earn a medical degree and then complete several years of residency training. In addition, dermatologists may then participate in a dermatology fellowship or complete additional, specialized training in a dermatology practice. If practicing in the United States, dermatologists must pass the United States Medical Licensing Exam (USMLE), become licensed in their state of practice, and be certified by the American Board of Dermatology.

Most dermatologists work in a medical office or private-practice setting. They diagnose skin conditions and rashes, prescribe oral and topical medications to treat skin conditions, and may perform simple procedures, such as mole or wart removal. In addition, they may refer patients to an oncologist if skin cancer that has metastasized is suspected. Recently, cosmetic procedures have also become a prominent part of dermatology. Botox injections, laser treatments, and collagen and dermal filler injections are popular among patients, hoping to reduce the appearance of skin aging.

Dermatology is a competitive specialty in medicine. Limited openings in dermatology residency programs mean that many medical students compete for a few select spots. Dermatology is an appealing specialty to many prospective doctors, because unlike emergency room physicians or surgeons, dermatologists generally do not have to work excessive hours or be “on-call” weekends and holidays. Moreover, the popularity of cosmetic dermatology has made it a growing field with many lucrative opportunities. It is not unusual for dermatology clinics to market themselves exclusively as cosmetic dermatology centers, and for dermatologists to specialize exclusively in these procedures.

Consider visiting a dermatologist to talk about why he or she entered the field and what the field of dermatology is like.