Skin rashes that occur on small sections of your body are often caused due to an external skin problem, such as an allergic reaction to a substance or material, localized skin inflammation or skin disease. Full body rashes can often signal the presence of an internal problem. There are 4 main causes of full body rashes: digestive system disorders, drug reactions, certain cancers and thyroid problems.
Digestive System Disorders
Many digestive system problems can cause rashes to develop across the body. These disorders include celiac disease, liver disease, anemia related to iron deficiency and kidney problems.
Celiac disease is a disorder in which an individual’s intestinal tract cannot absorb gluten protein from foods. The immune system treats gluten as a dangerous foreign body and reacts by destroying the villi lining the intestines. The destruction of the villi causes the person to become deficient in certain nutrients, and to experience symptoms such as seizures, fatigue and a characteristic itchy rash covering the body.
Both liver and kidney problems will cause body rashes since both of these organs are responsible for filtering toxic substances from the bloodstream. If either aren’t working , the substances can build up and cause persistent outbreaks across the body.
Anemia develops when the body has too few circulating red blood cells due to a lack of available iron. Again, the rash that occurs with this condition is thought to be due to a build-up of substances that the immune system reacts to.
There are many commonly prescribed medications that can cause allergic reactions that result in widespread rashes. These medications include both ingested and topical antifungal drugs, such as fluconazole, ketoconazole or clotrimazole; antibiotics like penicillin or cephalosporins; and some pain medications such as any oxycodone drugs or duloxetine. Chemotherapy drugs may also cause a full body rash.
Immune System Cancers
Cancers which affect the immune system, such as leukemia and lymphoma, can cause characteristic full body rashes. Individuals suffering from leukemia have small red, rash-like spots on their skin caused by blood leaking from the capillaries which lie just under the skin. People with lymphoma do not develop these spots; however, can suffer from extremely itchy, red skin.
A thyroid gland which produces too much of the thyroid hormone can lead to a condition known as Graves’ dermopathy; a widespread, lumpy skin rash. Similar to the other causes of full body rashes, this often develops with the immune system attacks the thyroid gland causing the balance of the hormones it produces to shift.