Antihistamines. These medications counter the effects of histamine, the substance that makes eyes water and noses itch and causes sneezing during allergic reactions. Sleepiness was a problem with the oldest antihistamines, but the newest drugs do not cause such a problem. Antihistamines come as pills or nose sprays.

Allergic reactions can be treated in various ways. Prevention of allergic reactions can be achieved by desensitization (hyposensitization) therapy, which can be used to reduce the hypersensitivity reaction through repeated injections of allergens. Extremely dilute concentrations of known allergens (determined from the allergen tests) are injected into the patient at prescribed intervals (e.g., weekly). The quantity of allergen delivered by the shots is slowly increased over a buildup period until an effective dose is determined and that dose is maintained for the duration of treatment, which can last years. Patients are usually encouraged to remain in the doctor’s office for 30 minutes after receiving the injection in case the allergens administered cause a severe systemic reaction. Doctors’ offices that administer desensitization therapy must be prepared to provide resuscitation and drug treatment in the case of such an event.

Desensitization therapy is used for insect sting allergies and environmental allergies. The allergy shots elicit the production of different interleukins and IgG antibody responses instead of IgE. When excess allergen-specific IgG antibodies are produced and bind to the allergen, they can act as blocking antibodies to neutralize the allergen before it can bind IgE on mast cells. There are early studies using oral therapy for desensitization of food allergies that are promising. These studies involve feeding children who have allergies tiny amounts of the allergen (e.g., peanut flour) or related proteins over time. Many of the subjects show reduced severity of reaction to the food allergen after the therapy.

There are also therapies designed to treat severe allergic reactions. Emergency systemic anaphylaxis is treated initially with an epinephrine injection, which can counteract the drop in blood pressure. Individuals with known severe allergies often carry a self-administering auto-injector that can be used in case of exposure to the allergen (e.g., an insect sting or accidental ingestion of a food that causes a severe reaction). By self-administering an epinephrine shot (or sometimes two), the patient can stem the reaction long enough to seek medical attention. Follow-up treatment generally involves giving the patient antihistamines and slow-acting corticosteroids for several days after the reaction to prevent potential late-phase reactions. However, the effects of antihistamine and corticosteroid treatment are not well studied and are used based on theoretical considerations.

Treatment of milder allergic reactions typically involves antihistamines and other anti-inflammatory drugs. A variety of antihistamine drugs are available, in both prescription and over-the-counter strengths. There are also antileukotriene and antiprostaglandin drugs that can be used in tandem with antihistamine drugs in a combined (and more effective) therapy regime.

Treatments of type III hypersensitivities include preventing further exposure to the antigen and the use of anti-inflammatory drugs. Some conditions can be resolved when exposure to the antigen is prevented. Anti-inflammatory corticosteroid inhalers can also be used to diminish inflammation to allow lung lesions to heal. Systemic corticosteroid treatment, oral or intravenous, is also common for type III hypersensitivities affecting body systems. Treatment of hypersensitivity pneumonitis includes avoiding the allergen, along with the possible addition of prescription steroids such as prednisone to reduce inflammation.

Treatment of type IV hypersensitivities includes antihistamines, anti-inflammatory drugs, analgesics, and, if possible, eliminating further exposure to the antigen.

Antihistamines are the most frequently used and widely available medications for motion sickness; nonsedating ones appear to be less effective. Antihistamines commonly used for motion sickness include cyclizine, dimenhydrinate, meclizine, and promethazine (oral and suppository). Other common medications used to treat motion sickness are anticholinergics such as scopolamine (hyoscine—oral, intranasal, and transdermal), antidopaminergic drugs (such as prochlorperazine), metoclopramide, sympathomimetics, and benzodiazepines. Clinical trials have not shown that ondansetron, a drug commonly used as an antiemetic in cancer patients, is effective in the prevention of nausea associated with motion sickness.

Medications in Children

Although using antihistamines to treat motion sickness in children is considered off-label, for children aged 2–12 years, dimenhydrinate (Dramamine), 1–1.5 mg/kg per dose, or diphenhydramine (Benadryl), 0.5–1 mg/kg per dose up to 25 mg, can be given 1 hour before travel and every 6 hours during the trip. Because some children have paradoxical agitation with these medicines, a test dose should be given at home before departure. Oversedation of young children with antihistamines can be life-threatening.

Scopolamine can cause dangerous adverse effects in children and should not be used; prochlorperazine and metoclopramide should be used with caution in children.

Approximately 33 percent of people experience a mild problem with motion sickness, whereas up to 66 percent experience motion sickness under extreme conditions, such as being on a tossing boat with no view of the horizon. Connections between regions in the brain stem and the autonomic system result in the symptoms of nausea, cold sweats, and vomiting.

The part of the brain responsible for vomiting, or emesis, is known as the area postrema. It is located next to the fourth ventricle and is not restricted by the blood–brain barrier, which allows it to respond to chemicals in the bloodstream—namely, toxins that will stimulate emesis. There are significant connections between this area, the solitary nucleus, and the dorsal motor nucleus of the vagus nerve. These autonomic system and nuclei connections are associated with the symptoms of motion sickness.

Motion sickness is the result of conflicting information from the visual and vestibular systems. If motion is perceived by the visual system without the complementary vestibular stimuli, or through vestibular stimuli without visual confirmation, the brain stimulates emesis and the associated symptoms. The area postrema, by itself, appears to be able to stimulate emesis in response to toxins in the blood, but it is also connected to the autonomic system and can trigger a similar response to motion.

Autonomic drugs are used to combat motion sickness. Though it is often described as a dangerous and deadly drug, scopolamine is used to treat motion sickness. A popular treatment for motion sickness is the transdermal scopolamine patch. Scopolamine is one of the substances derived from the Atropa genus along with atropine. At higher doses, those substances are thought to be poisonous and can lead to an extreme sympathetic syndrome. However, the transdermal patch regulates the release of the drug, and the concentration is kept very low so that the dangers are avoided. For those who are concerned about using “The Most Dangerous Drug,” as some websites will call it, antihistamines such as dimenhydrinate (Dramamine®) can be used.

Complementary approaches marketed for preventing or treating motion sickness include acupressure, magnets, ginger, pyridoxine, and homeopathic remedies.

Acupressure and Magnets

Research does not support the use of acupressure or magnets for motion sickness.

Ginger

Although some studies have shown that ginger may ease pregnancy-related nausea and vomiting, there is no strong evidence that it helps with motion sickness.

Homeopathic Products

There is no evidence supporting claims that homeopathic products prevent or alleviate motions sickness.

Pyridoxine (Vitamin B₆)

Although an American College of Obstetricians and Gynecologists 2015 Practice Bulletin Summary recommends pyridoxine alone or in combination with doxylamine (an antihistamine) as a safe and effective treatment for nausea and vomiting associated with pregnancy, there is no evidence supporting claims that pyridoxine prevents or alleviates motion sickness.

Safety

• In some people, ginger can have mild side effects such as abdominal discomfort. Research has not definitely shown whether ginger interacts with medications, but concerns have been raised that it might interact with anticoagulants. The effect of using ginger supplements with common over-the-counter drugs for motion sickness is unknown.
• Taking excessive doses of pyridoxine supplements for long periods of time can affect nerve function.

We should all be thankful to have some histamine in our bodies. This chemical messenger helps our brains stay alert, lets our stomachs dissolve food and powers our immune systems to root out and kill infectious parasites. However, anyone who suffers from minor to severe allergies knows histamine can have a dark side, too.

What are cold and cough medicines?

Cold and cough medicines can help relieve symptoms of a common cold. The symptoms of a cold can include a sore throat, stuffy or runny nose, sneezing, and coughing.

You don't usually need to treat a cold or the cough that it causes. You can't cure a cold, and antibiotics won't help you get better. But sometimes the symptoms can keep you awake or cause a lot of discomfort. In that case, cold and cough medicines can sometimes be helpful.

What are the different types of cold and cough medicines?

There are lots of different cold and cough medicines, and they do different things:

• Nasal decongestants - unclog a stuffy nose
• Cough suppressants - quiet a cough
• Expectorants - loosen mucus in your lungs so you can cough it up
• Antihistamines - stop runny noses and sneezing
• Pain relievers - ease fever, headaches, and minor aches and pains

What do I need to know about taking cold and cough medicines?

Before taking these medicines, read the labels and follow the instructions carefully. Many cold and cough medicines contain the same active ingredients. For example, some of them include pain relievers. If you are taking these medicines and are also taking a separate pain reliever, you could be getting a dangerous amount of the pain reliever.

Do not give cold or cough medicines to children under two, and don't give aspirin to children.

What else can I do to feel better for a cold or cough?

If you decide that you don't want to take cold and cough medicines, there are other ways to feel better:

• Drink lots of fluids
• Get plenty of rest
• Use a cool mist humidifier
• Use saline nose drops or sprays
• Use nasal suctioning with a bulb syringe, which can be very helpful in children under a year old