The first step in controlling allergies is allergen avoidance.
General measures such as the use of soothing creams and wet wrapping can help allergic skin disease.
Drugs are effective in the control and treatment of allergic diseases but do not cure the underlying allergy.
The type of drugs, their names, and whether or not they are available without prescription, varies from country to country.
Drugs and therapy used to treat allergies can be divided into broad groups:
- Drugs that block the activity of chemicals that are released in the body during allergic reactions - antihistamines and leukotriene antagonists;
- Drugs which relax the constricted muscle around the airways of the lungs, or shrink congested tissue, or reverse the effects of the chemicals released during allergic reactions - bronchodilators, decongestants and epinephrine;
- Drugs that prevent the activation of cells that are involved in the allergic reaction - anti-allergic agents;
- Drugs which possess a more general action in reducing inflammation - corticosteroids;
- Therapy which modifies the immune response - allergen immunotherapy.
These drugs can be purchased as tablets, syrups or nasal sprays. They work by blocking the inflammatory effects of histamine, one of the major chemicals that the body releases when it comes into contact with an allergen to which you are sensitized.
The newer, non-sedating and less-sedating antihistamines are safer than the older antihistamines, because they are less likely to cause drowsiness or sedation.
These drugs act by blocking the action of a group of chemicals, the leukotrienes, which constrict the muscles around the airways of the lungs. Like histamine, they are released during the allergic reaction mainly from cells in the body, mast cells, which are central to the triggering of the allergic reaction.
Bronchodilators are used to relieve the chest tightness and wheezing which are the immediate symptoms of asthma. They work by relaxing the smooth muscle of the airways of the lung. People suffering from occasional wheezing or tightness in the chest can safely use bronchodilators as a single therapy. If the chest symptoms are prolonged, bronchodilators must be used in conjunction with an anti-allergic or corticosteroid inhaler, which will treat the longer-term inflammation that underlies recurrent attacks of asthma.
Decongestants work by constricting the blood vessels in the nose and can be given as a nasal spray or as tablets to provide immediate relief of nasal blockage. The nasal sprays should not be used for more than 7 days as they can damage the tissues of the nose and cause worsening of symptoms, a condition known as "rhinitis medicamentosa."
This drug is the most effective treatment for the acute severe generalized allergic reaction known as "anaphylaxis." Epinephrine works by countering all the effects on the body of the sudden release into the bloodstream of histamine and the leukotrienes. These cause wheezing, vomiting, a widespread itchy rash and a life-threatening fall in blood pressure. Epinephrine is available as a single unit for self-administration by injection or via an automatic injection device which is triggered when pressed firmly against the skin. The preferred site for injection is into the muscle of the outside of the thigh.
These drugs work by preventing the release of histamine and other chemicals from cells in the body that play a key role in the allergic reaction, namely mast cells and eosinophils. These drugs have very few side effects, but are only of moderate potency and are best used to treat mild-to-moderate allergic disease. To be effective they need to be taken before you come into contact with an allergen. Because they are so safe they are often prescribed for children. The most commonly used drugs of this type are sodium cromoglycate and nedocromil sodium.
Corticosteroids are often called "steroids" and are then wrongly confused with the anabolic steroids which bodybuilders use.
Medicinal corticosteroids work by preventing the body from making the chemical messengers (called cytokines) which are responsible for prolonging the immediate tissue inflammation that occurs after allergen exposure. Corticosteroids are thus used for treating the long-term inflammation experienced in chronic conditions such as asthma, allergic skin conditions, hay fever and perennial rhinitis.
Corticosteroids can be taken by inhalation, for asthma, and as creams or ointments for allergic skin conditions. They can be given by nasal spray for hay fever and perennial allergic rhinitis. To avoid side effects, these inhalers and sprays are formulated to work on the surface of the nose or lung, and to be poorly absorbed into the bloodstream. Corticosteroids can be taken in tablet form, when they may be effective in treating multiple manifestations of allergic disease, for example in a patient suffering from asthma, allergic rhinitis and eczema.
Long-term use of high doses of corticosteroids, particularly when taken as tablets, can result in unwanted side effects. These include facial reddening and swelling, thinning and bruising of the skin, muscle weakness, peptic ulcer, osteoporosis, cataracts in the eye and reduced growth rate in children. Accordingly the prescribing of corticosteroids in tablet form is reserved for severe allergic conditions.
Injection Allergen Immunotherapy
Allergen immunotherapy involves the injection of increasing amounts of allergen under the skin until sensitivity to the allergen is decreased. Injections are first given two times a week or weekly and then monthly over a 3-5 year period. This treatment is very effective for bee, wasp, yellow jacket, hornet and ant venom allergy and for allergy to certain inhalant allergens such as grass, weed and tree pollen. Injection immunotherapy may also be of benefit in the management of cat, dog, dust mite and mold allergy. This type of treatment is the only form of therapy for allergic disease that can lead to complete resolution of symptoms without medications and, when administered to children, may prevent the development of further allergic disease. Because there is a risk of a severe allergic reaction happening immediately or shortly after injection, allergen immunotherapy must be administered in a medical center or office where there are appropriate medications and equipment available. Patients must remain under medical observation for 20 minutes or more (as determined by the prescribing physician) after an immunotherapy injection in case an allergic reaction occurs.
Sub-Lingual Oral Immunotherapy
This type of immunotherapy, in which allergen is administered under the tongue for two minutes and then swallowed, has been shown to be effective and is in use in some countries in Europe. However universal acceptance of this treatment requires further successful trials. The benefit of this treatment compared to injection allergen immunotherapy is the greater safety margin and the fact that it can be administered by the patient at home.
Medications in Development
Anti-IgE Antibody Treatment
This is a novel form of treatment in which antibodies directed against the main antibody which causes allergic disease (IgE) are injected and bind to IgE forming complexes which are then removed via the kidneys. The injected antibodies have been made to resemble human proteins (humanized), so that the body does not reject them. Initial trials have been encouraging, but it remains to be determined which patients will be ideal for this form of therapy.