Although many causes of leg ulceration have been reported over 70% are related to venous insufficiency associated with venous hypertension. Contact sensitivity (allergic contact dermatitis) is a frequent complication in patients with chronic venous leg ulcers affecting between 51–81% of patients. Complications associated with contact sensitivity in patients with non-healing leg ulcers are increased morbidity due to eczema and irritation which may result in delayed healing. This article reviews the frequency of contact sensitivity. Research has shown that lanolin and topical antibiotics, such as neomycin and framycetin, are the most common leg ulcer sensitizers and should be avoided in treatment. Creams have also been shown to contain sensitizers and therefore ointments should be used in preference to creams. The avoidance of allergens is important in the prevention of contact sensitivity and the promotion of ulcer healing.