There are many different causes of itching, and those causes are typically related to the type of itching being experienced. Itching is typically classified as random or chronic. Random itching is usually caused by something landing on the skin. It can be something tiny, such as a small insect or a hair. Skin disorders, allergic reactions, and some diseases typically cause chronic itching.
When particles land on the skin, nerve receptors send signals to the spinal cord, and then the spinal cord alerts the brain to send a "scratch" signal. The impulse to scratch often comes from a need to rid the body of a foreign substance. For instance, this happens when a bug crawls on the skin or a lock of hair tickles the neck. Scientists used to believe that the impulse to scratch came from the same receptors that cause pain reactions, but they eventually discovered that the impulses were completely different. Scratching impulses cause an aggressive response, while pain impulses cause a withdrawal.
Skin disorders that can be causes of itching include psoriasis, eczema, and dermatitis. All of these disorders typically include an itchy rash on the surface of the skin. Psoriasis is believed to be caused by a chemical imbalance in the skin, and may be genetic in its origins. Eczema is generally considered to be the result of environmental factors.
Some of the most common causes of itching are not directly associated with skin disorders and can include dry skin and topical allergic reaction. Dry skin usually begins to flake off, which can irritate the skin and lead to itching. Dry skin can usually be treated by a moisturizer. Allergens that are exposed to the skin can often lead to itching. Poison ivy and poison oak are some good examples, but the allergen that could trigger itching varies with each individual.
Causes of itching can also include certain types of parasites, such as lice and scabies. Lice is most often found in hair, but scabies can spread anywhere on the body. The parasites that cause scabies are microscopic and typically burrow under the skin. Both scabies and lice can be treated with over-the-counter medications.
In rare instances, the causes of itching may stem from a serious disease, such as hepatitis C or liver disease. Pregnant women should probably see a doctor if they begin to suffer from persistent itching, as it can indicate cholestasis, a condition that sometimes occurs late in pregnancy and can cause damage to the liver. It is probably a good idea to see a doctor for itching that does not respond to topical treatment within seven days.