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Author: Vanessa Ngan, Staff Writer, 2012.
Topical medications include any balm, cream, gel, oil, lotion, patch, ointment or any other product with a medicinal ingredient that is applied to the skin.
A topical medication is made up of an active ingredient and base which may contain preservatives and fragrances. Many topical formulations are available over-the-counter and include products such as antibacterial and antifungal preparations, anti-inflammatory and pain-relief preparations, and cleansing and moisturising agents.
An allergy to a topical medication can produce a range of reactions.
Some people may suffer from one or more reactions. In particular, atopic individuals (patients with atopic eczema, asthma and/or rhinitis) are more prone to irritant contact dermatitis, which in turn increases their likelihood of allergic contact dermatitis as their skin barrier function is weakened and more sensitised to the allergen.
Allergens found in topical medications may be the active drug ingredient or a component of the vehicle or base that carries the drug.
Drug allergens found in topical formulations that may cause allergic skin reactions include:
Allergy to a topical medication is diagnosed by performing special allergy tests, called patch tests. Diagnosis may involve testing against the active drug ingredient or a component of the base. See individual contact allergens for patch testing recommendations.
It appears that allergy to topical medications is more common in elderly patients. A study of all patients patch tested at a Sheffield hospital over 9 years confirmed that contact allergy to topical medicaments is more common in those aged more than 70 years compared with the younger age groups.
Some patients with pre-existing skin conditions may be more at risk of developing allergic reactions to topically applied medications.
Contact dermatitis should clear rapidly once the offending allergen is removed. In cases where the allergen is not a topical corticosteroid, over-the-counter mild topical steroids, such as hydrocortisone 0.5–2.5%, may be used to help control itching, swelling, and redness. In more severe cases, a prescription steroid cream may be required, as well as antibiotic medication if the skin becomes blistered and infected (impetiginised).
Care needs to be taken when prescribing a topical medication to elderly patients with eczema, especially for preparations that contain perfumes, lanolins (wool alcohols), and local anaesthetics as these are the allergens most commonly associated with allergic skin reactions in this group of patients.
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