The largest and most accessible organ in the human body, skin is vulnerable to a variety of influences that can lead to disease. Some skin diseases are predetermined by an individual's genetic inheritance. Others can be caused by exposure to a harmful foreign substance. Still others can result from unhealthy personal habits. Knowledge of the different types of skin disease is important for those who seek to maintain the health of this vital organ.
Cancer
The damaging influence of ultraviolet rays on skin is well documented. Overexposure to the sun's rays increases the risk of skin cancers.
The outer layer of skin, called the epidermis, is composed of 3 layers. The outer layer of the epidermis is made up of dead cells called keratinocytes. Living cells called squamous cells make up the second layer. The third, and deepest, layer of the epidermis consists of basal cells. Basal and squamous cell carcinomas are the most common skin cancers, according to the Centers for Disease Control and Prevention. These cancers are largely curable.
Melanoma, the third most common skin cancer, is more dangerous and difficult to treat. It arises from melanocytes, which are cells in the epidermis that contain pigment. Treatment for melanoma requires surgery, chemotherapy or radiation therapy.
Inherited Diseases
A genetic predisposition can cause skin disease. The National Psoriasis Foundation explains that psoriasis is likely linked to several different genes. The characteristic red, scaly patches of psoriasis flare up when certain environmental influences, such as stress or infection, exacerbate, or magnify, a genetic predisposition to the disease.
Genetic diseases that primarily affect other organ systems can also have skin-related components. Crohn's disease is characterized mainly by its inflammatory influence in the small intestine, but DermNet NZ mentions that it also causes skin lesions in 40 percent of patients.
Infectious Diseases
A fungus, bacteria or virus can infect the skin. Parasitic plants and animals that feed on dead tissue cause fungal infections, such as ringworm. Viral infections such as chicken pox affect those without vaccination or exposure to the virus. Skin that is dry and cracked is more vulnerable to bacterial infections, such as cellulitis, because bacteria can more easily invade the compromised epidermis.
Allergic Reactions
Allergic reactions can cause swelling, redness, itching and blisters on the skin. Allergic skin reactions are caused by ingestion of an allergen through the mouth or lungs or by physical contact with an allergen, a condition known as allergic contact dermatitis. The American Academy of Allergy, Asthma and Immunology lists many allergens that commonly cause allergic skin reactions, including medications, foods such as eggs and peanuts, latex products, metals used in jewelry or clothing fasteners and plants.
Allergic reactions range from mild to severe. In worst-case scenarios, allergic skin reactions can lead to anaphylactic shock, a life-threatening allergic reaction that can cause the airway to constrict.
