Skin rash on lower leg

Definition

A skin rash (exanthema) describes a temporary irritation of the skin, which can have various causes and appear in many different ways. The reddened areas of skin can be covered with nodules, crusts, spots, blisters, scales or wheals. They are usually caused by an allergy or infection or as a result of a side effect of medication.

Causes

Skin rashes are often allergic. In this case it is important to ask if, for example, a new cream has been used for the legs or if the rash has appeared after wearing new boots/other clothes. Intolerance to medication can lead to a rash affecting not only the legs but the whole body.

A rash can also be a sign of a skin disease. Neurodermatitis mainly affects the back of the knees, elbows and neck, while psoriasis occurs mainly on the shins, elbows and head. Shingles can also be a locally very limited skin condition on the legs.

In rare cases, a small spotty, knotty HIV-related skin rash on the legs can also appear. Often this only affects the trunk of the body and/or the face. A characteristically circular, growing skin rash on the lower leg can be a sign of an infection with Lyme disease.

This is transmitted by ticks. A further frequently occurring skin rash on the lower leg is erysipelas. This is a bacterial infection of the skin.

The bacteria use tiny injuries of the skin as an entry point and spread via the lymph vessels or the intercellular space. If painful reddish papules preferably appear on the shinbone, it can also be erythema nodosa. This special skin condition can occur in connection with sarcoidosis or in the context of Crohn’s disease. Insect bites can also lead to skin rashes on the lower leg.

Diagnosis

In order to find the cause of a new skin rash, it is important that the doctor takes a close look at the rash, as often the very characteristic appearance can already lead to a diagnosis. It is also important to know whether the rash has changed over time, whether it is spreading, whether there is itching and whether there are accompanying symptoms such as fever. Under certain circumstances it may be necessary to take a sample of the affected skin area or to carry out allergy tests.