Dermatitis

MPHA6508COMMUNITY PHARMACY Dermatitis-Irritant Contact Dermatitis-Allergic Contact Dermatitis

Learning outcomesAt the end of the lectures, the studentsshould be able to:Identify the types of irritants which causes contact dermatitis.Differentiate between Irritant Contact Dermatitis and Allergic Contact Dermatitis.Offer appropriate pharmacological and non-pharmacological advice to patients.Identify if there is a need for referral.

DermatitisCharacteristics:SoreRedRashPain or itchIn primary care, the two most common formsof dermatitis are:Irritant contact dermatitisAllergic contact dermatitis

Distribution of contact dermatitis

Allergens & Irritants known to precipitate dermatitis

ContinueICD is more common than ACD.ICD has been reported to account for 80% of all occupational skin disorders.

AetiologyIn ICD an agent must penetrate the outer layer of the skin (stratum corneum) to invoke a physiological response.Factors that affect the severity of the reaction - type of irritant - concentration of the irritant - quantity of the irritant - length of exposure to the irritant - Skin susceptibility (eg. thick, thin, oily, dry, very fair, previously damaged skin or pre-existing atopic tendency)

Irritant Contact Dermatitis(ICD)The contact substances to cause primary irritable contact dermatitis are strong irritable, such as strong acid and strong base, etc.Dermatitis can happen in any person after contact with the substance. The skin erupts when it encounters certain irritants, such as chemicals that directly damage the superficial layer of the skin. The damage occurs more readily in people with constantly wet hands.People with atopic dermatitis are more prone to ICD.

ContinueICDA reaction can be seen with a single or frequent exposure to the irritant.In ICD, the incubation period between the exposure and the onset of symptoms is minutes to hours.Eg. A single exposure to strong acids can produce ulceration.A repeated exposure to zinc oxide tape can cause a prickly heat type of dermatitis.

ICD is more common than ACDICD has been reported to account for 80% of all occupational skin disorders.

Example of ICDDribble rash around the mouth or on the chin in a baby, or in older children due to licking; the cause is saliva, which is alkaline. Skin bacteria may contribute to the clinical appearance.Dermatitis on a finger underneath a ring. Soaps,shampoos, detergents and hand creams may accumulate under the ring and cause irritant contact dermatitis.Fibreglass may cause direct mechanical/frictional damage.

Example of ICD

Example of irritantsCommon skin irritants are soaps and detergents, disinfectants and cleaning chemicals, shampoos, dyes, foodstuffs and cutting oils (low-grade irritants/chemical irritants).

As a consequence, irritant contact dermatitis is often job-related; hairdressers, cooks and caterers, dish-washers, machine-tool operators, nurses and homemakers are all at risk.

Allergic Contact Dermatitis(ACD)In ACD, the onset of signs & symptoms can be seen within a few days of exposure, in areas that are exposed directly to the allergens.A minimum of 10 days is required for individuals to develop specific sensitivity to a new contactant. Eg. an individual who never has been sensitized to poison ivy may develop only a mild dermatitis 2 weeks following the initial exposure but typically develops severe dermatitis within 1-2 days of the second and subsequent exposures.

ACDInitially requires sensitisation to occur.This leads to specific cell-mediated sensitisation.Once the skin has become sensitised to an allergen, re-exposure to the allergen triggers the T cells memory to initiate an inflammatory response 24-48 hours after re-exposure.One is not born with this type ofallergy- a person must has previously come into contact with the allergen which has sensitised his immune system. Once sensitised, his skin reacts and becomes inflamed when it comes into further contact with the allergen. This is why a person can suddenly develop a skin allergy to something he has come into contact with many times before. The allergic reaction can be seen at any site of the body and it is not limited to the site of the exposure only.

Areas of ACD and Causes

ACDThe condition is caused by direct contact with the trigger agent or allergen.The contact substances are not irritable, but a few people can be allergic to the substances.After contacting to the substances again (re-exposure), dermatitis can happen in the contact region or the nearby region 12-48 hours later. One can expect the symptoms to disappear if this substance is kept from reaching the skin.The patch test is the only useful and reliable method for the diagnosis of ACD.

Allergic contact dermatitisAllergy to leathercomponents in a hatband. Allergy reaction caused by wearing sandalsAllergy to nickel in jewellery

Example ACDAllergy to lacquerAllergy to lacquerAllergy to substances in wrist watch

Irritants in ACDNickel - this is the most common cause. Nickel occurs in many types of metal. For example: jewellery, studs in jeans and other clothes, bra straps. It is common to develop itchy red patches on the skin next to such things.Cobalt - traces of this metal may be found in some jewellery.Cosmetics - particularly perfumes, hair dyes, preservatives and nail varnish resins.Additives to leather and rubber (in shoes, clothes, etc).Preservatives in creams and ointments.Plants - the most common - chrysanthemums, sunflowers, daffodils, tulips and primula.

Arriving at a differential diagnosisGenerally, it is difficult to identify the cause due to the similar clinical features of both ICD and ACD.Treatment is generally the same for both.Asking symptom-specific questions will help pharmacist to determine whether a referral is needed or not.

Clinical featuresBoth ICD and ACD generally has similar clinical features.Skin appears red, itchy, inflamed and might show papules and vesicles at the site of the direct contact of the inciting substances.

Clinical features of ACD and ICDIn acute condition - well demarcated erythema, weeping or blisters.In subacute condition - less well demarcated erythema, maybe scaly skin.In chronic condition erythema and dry, thick, scaly skin.

Differences ACD vs ICD