Corticosteroids are a class of drugs related to the stress hormone cortisol. Like all hormones, they have wide-ranging effects on the body; the major effect that makes them effective for allergies is reducing the immune response. They are unrelated to anabolic steroids, the substances notorious for sometimes being abused by athletes.
For allergies, corticosteroids may be found in nasal sprays to treat allergic rhinitis, such as fluticasone (Flonase) and mometasone (Nasonex). Unlike nasal decongestant sprays, which can cause rebound congestion when discontinued, nasal corticosteroid sprays are generally safe for long-term use.
Corticosteroid eye drops such as prednisolone and dexamethasone may be prescribed to treat severe eye symptoms such as allergic conjuctivitis and red, watery eyes caused by hay fever. They can lead to eye infections with extended use.
Many corticosteroids of varying potencies are available as creams and ointments to treat atopic dermatitis (eczema), a chronic red, scaly rash. Mild ones such as hydrocortisone can be obtained OTC, while stronger ones such as betamethasone require a prescription.
Oral corticosteroids such as prednisone can have severe short-term and long-term side effects, and are used by prescription only in very severe cases of allergy. They may be used as a rescue medication for asthma attacks.
Leukotriene modulators block the action of the body chemical leukotriene. They ease bronchoconstriction in asthma and seasonal allergies, and also treat both seasonal and perennial allergic rhinitis (hay fever). These are oral medications that are not intended as rescue medications for asthma attacks; rather, they are intended to reduce the frequency and severity of bronchoconstrictino. Leukotriene modulators include montelukast (Singulair) and zileuton (Zyflo).
Mast Cell Stabilizers
Cromolyn sodium, also called cromoglicic acid, is a mast cell stabilizer. Mast cells normally contain histamine stored in little packets called granules. When triggered by an allergen, mast cells release the histamine in a process called degranulation. Cromolyn sodium prevents degranulation and thus stops histamine from being released.
Cromolyn sodium is administered as an OTC nasal spray. It can take up to two weeks to reach full effectiveness.
The medications described so far are aimed specifically at allergies. A few other medications in classes not primarily directed at allergy treatment have found use for certain allergic symtpoms.
Doxepin is used as an antipruritic. Taken orally, it has psychotropic properties, but when applied topically it reduces itching.
Ipratropium is sometimes used in inhalers to treat asthma. It falls into a class of medications called anticholinergics, meaning it blocks the neurotransmitter acetylcholine.