Adverse Reactions to Topical Therapy

Adverse Reactions to Topical Therapy

These are due to either irritation or allergy and can be difficult to differentiate clinically, although immediate stinging sensations are likely to be irritant in nature.
Irritant reactions can affect anyone, although are more likely to occur in atopic subjects who tend to have a dry sensitive skin. They are more common with creams, which contain preservatives.
Allergic reactions are less common and involve the immune system via a Type IV delayed hypersensitivity reaction, which can be investigated by patch testing. They should be suspected if the skin condition worsens or extends to other areas while on treatment.
Any topical therapy can cause an allergic reaction, although some are more likely than others, particularly topical antihistamines, local anaesthetics and antibiotics. The reaction may be due to the active ingredient, eg hydrocortisone or neomycin, or to an excipient, eg a preservative or emulsifier. All ingredients are listed in the Summary of Product Characteristics and Patient Information Leaflets.