The skin is the body's largest organ. This protective covering keeps out germs, helps hold muscles and organs in place, and aids in the absorption of vitamin D from the sun. With so large an area of body space to cover, the opportunities for skin to become irritated are widespread and manifold. Determining the causes of skin irritations such as hives and itching can be a difficult process.
Allergic Urticaria
When the human body experiences an allergic reaction to a common substance such as food or medicine, hives can result. Hives, also referred to as urticaria, are red, itchy swollen patches of skin that are short-lived. Hives last for 24 hours at most, according to the Allergy and Asthma Foundation of America.
Allergic reactions occur when the body mistakenly identifies a substance as harmful. In response, cells release chemicals called histamines, which increase blood volume and increase the permeability of blood vessel walls. This allows fluids to flow into the affected area and causes the inflammation associated with hives.
Pressure Urticaria
Some people are prone to getting hives on areas of the body that are subject to prolonged periods of increased pressure. For these individuals, extended periods of sitting can cause hives on the buttocks, while overly tight clothing results in hives in the areas where the skin is constricted.
Cholinergic Urticaria
The common phrase "breaking out in hives" is often used to describe a situation in which a person undergoing anxiety experiences the occurrence of hives. This condition is known as cholinergic urticaria. This type of hives can also occur after exercise and in situations in which higher than normal weather temperatures are a factor.
Eczema
Eczema is common in children. It characteristically causes dry, scaly bumps around the elbows and knees. More serious cases can involve the entire body. Eczema is an allergic reaction and is commonly triggered by animal dander, dust, stress and soap, according to the American Academy of Allergy, Asthma and Immunology.
Seborrheic Dermatitis
Adults who suffer from occurrences of itchy, red, oily rashes around the nose, eyebrows or hairline may be experiencing the symptoms of seborrheic dermatitis. This condition is caused by the overproduction of oils from the sebaceous glands, which are located in the skin. Seborrhea manifests in infants as "cradle cap," which causes dry scaly skin over the scalp.
Contact Dermatitis
The American Academy of Family Physicians reports that a scaly red rash that occurs in an area of skin that has touched a foreign object or substance could be contact dermatitis. This is an allergic reaction and is often triggered by chemicals in cosmetics, certain types of metal used in jewelry or contact with plants to which the individual is sensitive.
