Contact Dermatitis

Question 1

What are the 2 main types of contact dermatitis?

Answer 1

Irritant contact dermatitis

Allergic contact dermatitis

Question 2

Is irritant contact dermatitis common?

Answer 2

Yes

Question 3

Where is irritant contact dermatitis typically seen?

Answer 3

On the hands

Question 4

How does irritant contact dermatitis present?

Answer 4

Well demarcated red patch with a glazed surface
May be swelling, blistering and scaling of the damaged area
Weeping precedes dry fissuring
Can be very itchy
Usually confined to site of contact with irritant

Question 5

What common irritants are there?

Answer 5

Detergents
Soaps
Oils
Solvents
Alkalis 
Water (if repeated)

Question 6

Why does irritant contact dermatitis occur?

Answer 6

Occurs whenever chemicals or physical agents damage the surface of the skin faster than the skin can repair itself.

Irritants remove the oil and moisture for the outer skin layer, allowing chemical irritants to penetrate more deeply and cause inflammation

Question 7

Who is mostly affected by irritant contact dermatitis?

Answer 7

Cleaners
Hairdressers
Food handlers
Bar staff

Question 8

What percentage of occupational hand dermatitis are due to irritants?

Answer 8

80%

Question 9

Can irritant and allergic contact dermatitis coexist?

Answer 9

Yes

Question 10

What are some typical examples of irritant contact dermatitis?

Answer 10

Dribble rash - saliva is alkali 
Napkin dermatitis - urine and faeces can affect older incontinent patients as well as babies
Under a ring - build up of soap, creams 
Dry cold air 
Cosmetics may irritate sensitive skin 
Excessive water exposure

Question 11

How is iriritant contact dermatitis managed?

Answer 11

Avoidance of responsible substance
Wear suitable gloves to protect against irritants
Emollient creams
Topical steroids for acute flare ups

Question 12

What is allergic contact dermatitis?

Answer 12

A form of dermatitis caused by an allergic reaction to an allergen in contact with the skin. The allergen is harmless to people who are not allergic to it

Question 13

What type of hypersensitivity reaction is allergic contact dermatitis?

Answer 13

Type IV

Question 14

What are some common allergens that cause allergic contact dermatitis?

Answer 14

Nickel
Cement 
Leather
Perfumes, soaps, cosmetics
Rubber 
Latex 
Topical antibiotics 
Plants - poison ivy 
Hair dye 
Rosin (in adhesive plasters)

Question 15

Allergic contact dermatitis to topical antibiotics is common in…

Answer 15

Those over 70

Question 16

What are the clinical features of allergic contact dermatitis?

Answer 16

Arises hours after contact
May extend outside the contact area or become generalised
Intensely pruritic, erythematous, papular rash
May have vesicles and serous oozing if severe

Question 17

How is allergic contact dermatitis diagnosed?

Answer 17

Can be easy to recognise clinically and no specific tests required
Patch tests

Question 18

What is the treatment for allergic contact dermatitis?

Answer 18

Avoidance
Wear gloves
Emollient cream
Oatmeal bath, soothing lotions e.g calamine
Wet dressing
Topical steroids
Topical or oral antibiotics for secondary infection
Oral steroids in severe cases (short course)
Phototherapy

Question 19

What is the pathophysiology of allergic contact dermatitis?

Answer 19

Type IV delayed hypersensitivity reaction occurring 48-72 hours after exposure to allergen.

1) sensitisation - antigen penetrates skin - uptake by langerhans cell, irrational to lymph node and formation of sensitised T lymphocytes
2) repeated contact with antigen - CD4+ T cell recognises antigen on antigen presenting cell - release of inflammatory cytokines