Allergies

Contact Dermatitis Causes, Symptoms And Diagnostics

Contact Dermatitis causesDermatitis is an inflammation of the skin. Contact dermatitis is a localized irritation or rash of the skin which develops upon direct contact with a particular substance. Depending on the causative agent, contact dermatitis is of two types namely, irritant contact dermatitis and allergic contact dermatitis. In some cases, both the types can affect an individual at a time. It is estimated that irritant contact dermatitis is more common than allergic type. Nearly 75% of all contact dermatitis tend to affect the hands. The following article gives a detailed description of contact dermatitis including types, causes, symptoms and diagnostics.

Contact Dermatitis Causes

There are two types of contact dermatitis. Here are the causes of the both irritant and allergic contact dermatitis.

Irritant Contact Dermatitis

– This is caused from coming in contact with a substance that directly damages your skin. It can happen over acute (short) or chronic (long) time period.

Acute Irritant Contact Dermatitis
This is caused up on a single exposure to the foreign substance. A course of events happen within minutes to hours after getting exposed.

  • The irritant substance penetrates into the skin.
  • The substance harms the membranes of the skin cells.
  • The cell damage stimulates release of certain chemicals, which trigger the action of the immune system. The chemicals released are prostaglandins, lysozymes, kinins and histamines. This reaction is known as inflammatory response.
  • These chemicals also called inflammatory mediators increase the flow of blood.

Chronic Irritant Contact Dermatitis
This is caused due to multiple exposures to various irritants over time. It can take several months to years for the symptoms to occur. A course of events that happen include:

  • On each exposure, the outer layer of the skin disrupts gradually.
  • The inflammatory mediators are even released on each exposure.
  • The epidermis i.e the top skin layer thickens gradually.
  • The fat (lipid) layer of skin is damaged.
  • The affected skin thus loses the ability to protect the body and further exposure to the irritant damages the skin very badly.
  • The skin therefore becomes dry, thickened and scaly.
Allergic Contact Dermatitis

– Also known as ‘delayed hypersensitivity reaction’ or ‘type IV’, this is a type of immune reaction. One of the main feature of this type is a delay between the first exposure to a particular allergen and following reaction. This happens in two stages namely sensitization and elicitation.

  • Sensitization Phase
    This begins with the penetration of the substance into the skin, followed by binding to a type of skin immune cells, called Langerhans’ cells. The allergen substance then leaves the skin and enters to the lymph nodes present in the surrounding region. The allergen binds to T-lymphocytes, which is another type of immune cell. Here it proliferates and produces memory cells which can recognize the particular allergen.
  • Elicitation Phase
    This is followed by sensitization phase where the repeated exposure to the allergen makes the T-lymphocytes recognise them, activate and cause their multiplication. Inflammatory mediators bring more and more T-lymphocytes to the exposure site and this ongoing immune reaction causes eczema like inflammation at the site of skin contact. Even minute amounts of allergen are enough to cause inflammation. This phase takes place within 48 – 72 hours.

Symptoms of Contact Dermatitis

Symptoms range from mild dryness and redness to severe peeling and pain that will be very irritating.

Symptoms of irritant contact dermatitis include:

  • Stiff and tight feeling of skin
  • Mild swelling of skin
  • Painful ulcers on the skin
  • Blisters
  • Cracking and dry skin

Symptoms of Allergic Contact Dermatitis include:

  • Intermittent scaly and dry patches of skin
  • Reddening of skin
  • Itching or burning lesions
  • Blisters that ooze
  • Hives
  • Swelling of the face, eyes and genital regions
  • Darkened and cracked skin
  • Sun sensitivity

Diagnostics of Contact Dermatitis

To determine contact dermatitis, a physician asks certain questions like:

  • What are the present symptoms
  • When did the symptoms arise
  • Any other medical illnesses you are suffering from
  • Medications you are using
  • What skin care products you use

There are two differentiating features of contact dermatitis from other skin rashes that help in determining the disease condition – the time of onset and the site of the body that is affected.

Time of onset

  • Allergic contact dermatitis happens within 48 – 72 hours after exposure and the reaction increases and subsides depending on the allergen exposure.
  • Improvement of allergic reaction during holidays or weekends suggests occupational origin for the allergen substance.
  • Occurrence allergic reaction at weekends suggests environmental allergen.
  • Seasonal variation of contact dermatitis is observed with plant allergens which can be aggravated with light.

Body site
Contact dermatitis occurs only in the region that comes in contact with allergen or irritant substance. The pattern of the skin gives a clue of the substance that is causing allergy.

The physician then examines the rash and along with your answers, creates a general idea of what is the agent causing your symptoms. If the physician suspects it to be contact dermatitis, then he/she may suggest certain tests to diagnose the correct condition. Usually skin test, called patch testing is done.

Patch Test

– This test is performed in those who continue to suffer from symptoms even after undergoing through a trial of medications and avoidance. This helps in isolating the particular allergen that is causing allergic reaction.

A small amount of suspected allergen is applied to the skin and covered with a non-absorbent adhesive patch. This is removed after 48 hours to find if any reaction has occurred. If blistering, redness or hardness occurs, the test is considered to be positive indicating allergy to that particular substance. Some reactions may take more time, therefore the patch site is removed after 72 hours in such cases.

This gives you a clear explanation of contact dermatitis including the causes, symptoms and diagnostics.

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