Allergic rhinitis, allergic conjunctivitis, atopic dermatitis, urticaria, anaphylaxis and asthma (not included here; reviewed in Treatment Guidelines 2008; 6:83) are prevalent worldwide, especially in industrialized countries. Pharmacologic treatment of these disorders continues to improve in efficacy and safety. In addition to using drugs to prevent and control these allergic diseases, patients should be instructed to avoid, if possible, specific allergens and/or environmental conditions that trigger or worsen their symptoms. Allergen-specific immunotherapy may be useful for treatment of allergic rhinitis and allergic conjunctivitis, and in preventing severe insect venom-triggered reactions.

Cetirizine (Zyrtec, and others) and cetirizine/pseudoephedrine (Zyrtec-D) are becoming available without a prescription this month for treatment of allergic rhinitis and urticaria in adults and children. Cetirizine is the second of the second-generation H1-antihistamines to become available over the counter. Loratadine (Claritin, and others) was the first.

Cetirizine has been shown to be more effective than loratadine in suppressing histamine-induced wheals in healthy volunteers (W Carey et al. Drugs Exp Clin Res 2002; 28:243), but no well-controlled clinical trials have established that any second-generation H1-antihistamine is more effective overall than any other (M Plaut and MD Valentine. N Engl J Med 2005; 353:1934).

Cetirizine may be mildly sedating in some patients, but it is significantly less sedating than first-generation H1-antihistamines such as diphenhydramine (Benadryl, and others) or chlorpheniramine (Chlor-Trimeton, and others), which have been available without a prescription for many years. Its safety in young children is better documented than that of any other first- or second-generation H1-antihistamine (Treat Guidel Med Lett 2007; 5:71).

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Allergic rhinitis, allergic conjunctivitis, atopic dermatitis, urticaria, anaphylaxis and asthma (reviewed in Treatment Guidelines 2005; 3:33 and not included here), are prevalent worldwide, especially in industrialized countries. Pharmacologic treatment of these disorders continues to improve in efficacy and safety. In addition to using drugs to prevent and control the symptoms of their allergic diseases, patients should also be instructed to avoid, if possible, specific allergens and/or environmental conditions that trigger or worsen their symptoms.

Allergic rhinitis, allergic conjunctivitis, atopic dermatitis, urticaria and anaphylaxis, along with asthma (reviewed in Treatment Guidelines 2002; 1:7 and not included here), have increased in prevalence during the past 30 years and are now epidemic worldwide, especially in industrialized countries. Many safe and effective drugs are currently available for prevention and relief of symptoms in these disorders, but pharmacological treatment alone may not be sufficient. Patients should also be instructed to avoid specific allergens or environmental conditions that trigger their symptoms. Allergen-specific immunotherapy, parenteral administration of gradually increasing doses of the allergen ("allergy shots"), has been effective in allergic rhinitis, allergic conjunctivitis and allergic asthma, and also in prevention of anaphylaxis triggered by stings from bees, yellow jackets, hornets and wasps. It has not been effective in food allergy, atopic dermatitis or urticaria.

The FDA has approved the marketing of loratadine (Claritin - Schering), a second-generation H₁-antihistamine, without a prescription. The drug was also recently approved for OTC use as Alavert (Wyeth) and other generics are expected.

With the coming of spring, direct-to-consumer (DTC) advertisements in newspapers, in magazines and on television are urging people with seasonal allergies to ask their doctors about one or another of the newer, non-sedating antihistamines.

Cetirizine (Zyrtec - Pfizer), a histamine H 1 -receptor antagonist, has been approved by the US Food and Drug Administration for treatment of seasonal allergic rhinitis, perennial allergic rhinitis and chronic idiopathic urticaria in adults and children more than 12 years old.

Acrivastine/Pseudoephedrine (Semprex-D) for Seasonal Allergic Rhinitis (Burroughs-Wellcome), a combination of acrivastine with pseudoephedrine hydrochloride, has been approved by the US Food and Drug Administration for treatment of seasonal allergic rhinitis. Acrivastine is a new H 1 -receptor antagonist with a chemical structure similar to that of triprolidine (Actidil, and others) (RN Brogden and D McTavish, Drugs, 41:927, 1991). Pseudoephedrine is an α -adrenergic agonist. The combination is available only by prescription.

Loratadine (Claritin - Schering), a new H 1 -receptor antagonist, has been approved by the U.S. Food and Drug Administration for treatment of seasonal allergic rhinitis in patients more than 12 years old. It will compete with older, relatively sedating drugs such as chlorpheniramine (Chlor-Trimeton, and others) and clemastine (Tavist - Medical Letter, 35:9, 1993) and with newer relatively non-sedating agents such as terfenadine (Seldane) and astemizole (Hismanal).

Advertisements for clemastine (Tavist-1 - Sandoz), an ethanolamine oral antihistamine, have recently appeared on television and in major newspapers in the USA. Clemastine is an old drug (Medical Letter, 21:24, 1979) that has now become available without a prescription.

Astemizole (Hismanal - Janssen), a new antihistamine, was recently marketed in the USA for treatment of seasonal allergic rhinitis and chronic idiopathic urticaria. Like terfenadine (Seldane - Medical Letter, 27:65, 1985), astemizole is claimed to be no more sedating than placebo, but the new drug offers the advantage of a once-daily dosage schedule.