Others appear to produce allergy only in certain individuals who have a constitutional or
inherited predisposition to allergy.
(1) Urticaria. Urticaria (commonly called hives) is an allergic condition which
results in the formation of wheals (rounded or irregular shaped, transitory elevations of
the skin). Urticaria is usually caused by eating a substance to which the patient has
been sensitized, but may also be caused by a local allergen such as poison ivy; or it
might have a psychogenic origin. It is usually associated with much itching and may
cover the whole body. Often it is difficult to determine the cause, and the disease may
(2) Contact dermatitis. Contact dermatitis (dermatitis venenata) is due to
sensitization of the skin by direct contact with a sensitizing substance. The
development depends on how much of the substance is contacted, and how often. Why
sensitivity occurs is not known. At the beginning, the skin is reddened in the contacted
area, then raised lesions appear, and then blisters. The lesions may spread over the
body. The vesicles may become infected by bacteria, and pustules appear. There is
marked itching. The patient may carry the sensitizing substance to other skin areas by
his hands. The sensitizing substance may be almost anything. Examples include:
poison ivy, medicines, clothes, and soaps. A painstaking and thorough search is
necessary to find and remove the allergen. Treatment includes removal of the allergen,
mild bland applications, and antihistaminics in some cases.
(1) Psoriasis. Psoriasis is a chronic, recurrent disease of the skin,
characterized by reddish, rounded lesions that are covered by silvery scales. When a
scale is removed, it leaves a small bleeding point. The disease tends to begin on the
elbows, knees, or scalp, and to spread over the whole body.
(2) Acne vulgaris. Acne vulgaris is a chronic inflammation of the
sebaceous glands (oil glands) of the skin, which usually develops during adolescence.
Lesions develop rapidly and in crops, located mostly on the face, sometimes on the
sternal region, the shoulders, and the back. The lesions may cause considerable
scarring on healing. Treatment includes good personal hygiene to help prevent
secondary infections, dietary measures, antibiotics, and various skin lotions.
2-14. SIGNS AND SYMPTOMS OF SKIN DISEASE
a. Pruritis (Itching). The most common, most annoying, and least specific
symptom encountered in dermatologic conditions is pruritis. Among the causes of
itching may be included infectious agents, allergic conditions, neuroses, parasitic
infestations, dryness of the skin, anoxia of the skin, and chronic irritation of the skin.
The actual pathological change responsible for this symptom takes place in minute
nerve endings in the skin. The exact change is not known, but these endings become