Skin Rash

Contact dermatitis is inflammation of the skin (rash) that may result when the skin is touched by irritants or substances that cause an allergic reaction. Contact dermatitis can occur from exposure to many different compounds found both in the home and at work. There are two types of contact dermatitis:

Allergic contact dermatitis occurs when skin, which has become sensitized to a certain substance (allergen), comes in contact with that substance again
Irritant contact dermatitis occurs when the skin is exposed to a mild irritant (such as detergent or solvents) repeatedly over a long period of time or a strong irritant (such as acid, alkali, solvent, strong soap or detergent), which can cause immediate skin damage
Common sources of allergic contact dermatitis
Not everyone reacts to allergens. However, some people will react to an allergen which they had previously tolerated for many years. Skin can become allergic to a substance after many exposures or after just one exposure. Most people will have an allergic reaction to poison ivy after one exposure, for instance. This is a delayed skin reaction that typically develops 12 to 72 hours after exposure.

Common sources of allergic contact dermatitis include:
Nickel (a common metal used in jewelry) and other metals. Nickel has been reported to cause contact dermatitis in up to 10 percent of women. Gold is also becoming a widespread allergen. This type of allergic contact dermatitis can begin with intermittent rashes under earrings or other jewelry.
Fragrances – for example, those found in perfumes, soaps, lotions, and shampoos
Cosmetics
Topical medications such as antibiotics or anti-itch preparations – these cause worsening of the problem and are often misinterpreted as infection
Preservatives, which keep topical products from spoiling
Sunscreens – commonly cause a hive-like rash that can appear hours or days after sun exposure
Rubber ingredients – a common source of work-related allergy. Rubber can cause immediate allergic reactions, such as itching, burning, or welts. Some people experience itching and tearing eyes or even shortness of breath.
Common sources of irritant contact dermatitis
Detergents, soaps, cleaners, waxes, and chemicals are substances that can irritate the skin. They can wear down the oily, protective layer on the skin's surface and lead to irritant contact dermatitis. Irritant contact dermatitis is most common among people who regularly work with strong chemicals, such as restaurant, maintenance, and chemical workers.

Symptoms of Allergic contact Dermatitis and Irritant contact Dermatitis:

Allergic contact dermatitis

Reddening of skin (either in patches or all over the body)
Intermittent dry, scaly patches of skin
Blisters that ooze
Burning or itching that is usually intense without visible skin sores (lesions)
Swelling in the eyes, face, and genital areas (severe cases)
Hives
Sun sensitivity
Darkened, "leathery" and cracked skin
Allergic contact dermatitis can be very difficult to distinguish from other rashes.

Irritant contact dermatitis

Mild swelling of the skin
Stiff, tight feeling skin
Dry, cracking skin
Blisters
Painful ulcers on the skin