ANTIALLERGIC AGENTS relieve the symptoms of the allergic reaction that follows exposure to specific substances to which the patient is allergic. These substances may be endogenous or exogenous. Because allergic reactions generally cause release of the natural local hormone histamine, within the body, antihistamines are often very effective for the symptomatic relief of allergic reactions (see HISTAMINE H1-RECEPTOR ANTAGONISTS). For instance, allergic skin reactions to foreign proteins, contact-dermatitis, and insect stings and bites, show characteristic symptoms — including pruritus and erythaema — and these often respond well to treatment with antihistamines (including local application as a cream). On the other hand, some allergic reactions may cause marked inflammatory symptoms and here antihistamines may be insufficiently effective, and CORTICOSTEROIDS may be required. For example, in the treatment of atopic (allergic) bronchial asthma, long-term inhalation of corticosteroids may prevent asthma attacks and the associated bronchoconstriction and airways congestion. Similar antiinflammatory protection from the symptoms of allergic asthma may be achieved by chronic inhalation of one of a group of cromoglycate-related antiinflammatory substances which work by a mechanism that is not entirely clear — though they appear to prevent the release of histamine and other mediators. Examples are sodium cromoglycate and nedocromil sodium. Because allergic responses have an inflammatory component, ANTIINFLAMMATORY AGENTS may be used as adjuncts in antiallergic treatment. See also NSAID ANALGESICS.