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Allergic Skin Disease

There are 3 major skin diseases caused by allergies:

1. Eczema
2. Allergic Contact Dermatitis
3. Hives (Acute Urticaria)

It is important to remember that any combination of the 3 can occur in the same patient at the same or different times.

1. Eczema
Eczema is a common allergic skin disease in infants. It usually develops around 4 months of age. In some cases the term eczema is used interchangeably with dermatitis. Some prefer to reserve the term dermatitis, for cases of eczema caused by an external trigger, as in the case of allergic contact dermatitis.

In most cases, eczema resolves itself in infancy or at least by the time the child is 5 years old. It is usually the first symptom of the allergic march, often to be followed by asthma or hay fever, as seen in atopics. The symptom that occurs almost invariably in eczema is itching (pruritus). If this symptom is not present, the diagnosis of eczema should be seriously questioned. There are two forms of eczema. Acute eczema causes red, swollen patches on the skin, with watery discharge (oozing), and usually causes severe discomfort. Chronic eczema causes thickened, scaly skin patches, which often gets secondarily infected leading to crusting. As the term implies, chronic eczema tends to last, sometimes for years and in rare cases for life. In infants, eczema usually appears on the cheeks, scalp, neck and trunk. In children over two years old, eczema usually appears in the knee and elbow creases, the neck, wrists and ankles. However, there is overlap between the age groups, and other areas of the body may be involved.

-Factors affecting Eczema

The exact cause of eczema is unknown, but we do know some of the factors t hat precipitate or aggravate it. The main factor is heredity. About one-third of children with eczema have parents or close relatives who have eczema, asthma or hay fever (are atopic). Several studies have shown that, foods like milk, eggs, wheat, peanuts and soy are common causes of eczema in infancy. It is advisable to skin test all infants with severe eczema to these foods. Skin irritants, such as soaps, detergents and wool can all aggravate eczema. Climate can also trigger eczema. Babies who are brought from warm countries to areas where the climate is cold are particularly vulnerable. Cold, dry air causes the skin to become dry and itchy. A hot, humid climate can also cause sweating, which worsens the itching and scratching in eczema.

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2. Allergic Contact Dermatitis
This form of allergic skin disease occurs when a substance that comes in direct contact with the skin causes an eczematous reaction. It is usually impossible to tell the difference between atopic eczema and allergic contact dermatitis purely by examination of the rash. A thorough history and a suspicious, detective's mind is the most useful tool in helping to differentiate the two.

Poison Ivy is one of the most common and familiar causes of contact dermatitis. Other leaves such as oak and sumac can also cause contact dermatitis. The resin in the leaves is the offending agent.

Since new potentially sensitising chemicals are continually coming into use, the prevalence of allergic contact dermatitis will only continue to increase.

Contact dermatitis is the most common occupational disease, and as such, it is of tremendous importance to both the individual and society.

The diagnosis of Allergic Contact dermatitis is confirmed by doing a Patch Test. Allergens tested in the Standard Patch Test:

  1. Potassium Dichromate
  2. Neomycin Sulphate
  3. Thiuram mix
  4. Paraphenylendiamine
  5. Cobalt Chloride
  6. Benzocaine
  7. Formaldehyde
  8. Colophony
  9. Clioquinol
  10. Balsam of Peru
  11. N-Isopropyl-N-Phenyl parapheylendiamine
  12. Wool alcohols- Lanolin
  13. Mercapto mix
  14. Epoxy resin
  15. Paraben mix
  16. Partertiarybutyl-Phenol Formaldehyde Resin
  17. Fragrance mix
  18. Quaternium
  19. Nickel Sulphate
  20. 5-chloro-2-methyl-4-isothiazolin
  21. Mercaptobenzothiazole
  22. Sesquiterpene lactone mix
  23. Primin
  24. Alpha-amyl-chinnamaldehyde
  25. Compositae Mix
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3. Hives (Acute Urticaria)
Hives are itchy skin rashes with raised weals of different sizes. Sometimes they look like mosquito bites. They are sometimes referred to as urticaria. They may appear a few at a time or they may spread over the whole body. Hives tend to come and go and change places over the body. They last from minutes to days or may recur in crops for a period of weeks or months in different areas.

If hives last for more than six weeks they are called chronic urticaria. Hives lasting less than six weeks are known as asute urticaria.

Hives may affect the deeper layers of the skin and cause swelling. This is called angioedeama. Hives and angioedema may appear together or separately.

Hives can be caused by foods(especially milk, eggs, wheat, seafood, & peanuts), drugs like aspirin and penicillin, infections and inhaled subtances like cat hair and house dust mites. Physical agents like cold, heat sunlight, direct pressure, vibration and rubbing can also cause hives in some people. Insects like mosquitos, bed bugs and fleas can produce small crops of small itchy swellings on exposed parts of the body, sepecially the lower extremities in children. These may be a form of hives called papular urticaria.

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