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12-04-2012 | Immunology | Article

Insect bite remedies largely ineffective


Free abstract

MedWire News: There is little direct evidence for the efficacy of treatments for simple insect bites, conclude the authors of a review article in the UK Drugs and Therapeutic Bulletin.

They say that most bites need no treatment at all and warn against the routine use of steroid creams, antibacterial medications, and anti-itch preparations.

Background information in the review explains that insect bites can lead to local reactions, immune reactions including anaphylaxis, and secondary bacterial infections, such as impetigo or cellulitis.

Biting insects commonly encountered in the UK include midges, mosquitoes, biting flies, fleas, and bedbugs. The incidence of insect bites is seasonal, with many more occurring in the summer months when more skin is exposed and insects are active.

"Although insect bites are perceived to be common in the UK, the exact incidence is difficult to estimate since most are likely to go unreported: only those causing the more serious reactions are seen in primary care settings," the authors state.

UK guidelines for the management of insect bites are largely based on expert opinion and anecdotal experience rather than evidence.

"The management of simple insect bites is directed towards relieving the itching, pain and swelling," write the authors. "Although direct evidence of the efficacy of treatment for insect bites is often lacking, guidance may be justified on the basis of the established clinical effects of the drugs."

The review recommends that, for mild local reactions, the area should be cleaned and a cold compress applied to reduce pain and edema. Oral analgesics can be given for pain, while mild corticosteroid cream is helpful to reduce inflammation and itching.

In cases of large local reactions, oral antihistamines can be used, with nonsedating preparations being preferred during the day. Antibacterial treatment is not required for simple insect bites, but secondary infections should be treated with an oral antibacterial agent in accordance with local guidelines.

Creams containing local anesthetics or analgesics, such as lidocaine, benzocaine, or combined with antihistamines and antiseptics, are only "marginally effective and occasionally cause sensitization," the review notes.

In addition, there is no hard evidence to support use of the anti-itch lotion Crotamiton, and the British National Formulary notes that it is of "uncertain value." Similarly, calamine preparations are "of little value in insect bites and are not recommended."

Finally, the review warns that topical preparations may themselves cause allergic or sensitivity reactions that can exacerbate the original symptoms of the bite. "A good medical history is important to exclude this possibility when a patient presents with deterioration of their original symptoms," it advises.

By Joanna Lyford

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