The lesions itch and burn and appear between 30 minutes to several hours after the pressure. This phenonenon is often associated with chronic urticaria. The lesions occur after sitting on hard chairs, carrying bags, leaning against furniture, wearing seat belts and lying on hard mattresses. Swelling of the feet and hands, often indistinguishable from angiooedema, occurs after activities such as weight lifting, walking, jogging, and running. During severe attacks, arthralgias and a flu-like illness may accompany the rash.
Linear wheals appear as a result of scratching.
It may also be symptomatic of porphyria cutanea tarda. Patients notice erythema, burning, and urticarial wheals within minutes following exposure to sunlight. Wheals can develop anywhere on the body, mostly in the sun exposed skin. The action spectrum of solar urticaria is broad, ranging from UVC, UVB, UVA to visible spectrum. Avoidance of sunlight is important.