Contact dermatitis
Contact dermatitis is the inflammation (-itis) of the skin (derma) in response to contact with particular substances (allergens or irritants). The impacted area of the body depends on the site of contact. Inflammation usually clears up once the substance has been removed/avoided.
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Estimated by the International Workshop on Contact Dermatitis and the JAMA network found that 1 in 5 or 20% of the general population suffer from allergic contact dermatitis. [1,2]
NICE guidelines found that contact dermatitis accounts for 4–7% of dermatological consultations in secondary care.
Irritant contact dermatitis is more common than allergic contact dermatitis — up to 80% of contact dermatitis is irritant.
About two-thirds of all cases of contact dermatitis involve the hands.
Contact dermatitis tends to be most common in young females, this is due to an increased level of exposure to substances in jewellery (such as nickel) and cosmetics.
Between 13-34% of all occupational diseases are skin diseases; of these diseases, 90-95% are contact dermatitis. [3]
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Allergens
Cosmetics
Metals such as nickel or cobalt
Topical medicines such as topical corticosteroids
Rubber eg. latex
Textiles eg. dyes and resins
Strong glues
Some plants such as sunflowers, tulips, daffodils etc.
Irritants
Soaps and detergents
Disinfectants
Cement
Perfumes and toiletries
Powders, dust and soil [5]
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Medical Students
Types:
Allergic Contact Dermatitis (ACD): Triggered by allergens
Irritant Contact Dermatitis (ICD): Triggered by irritants
Allergic Contact Dermatitis:
Type IV hypersensitivity reaction (T cell-mediated, delayed)
Nickel sulphate is the most common allergen globally
Two main phases:
Sensitisation Phase:
Langerhans cells capture allergens and trigger the innate immune system
Antigens transported to lymph nodes
Presented to naive antigen-specific T cells
T cells undergo expansion and differentiation into memory/effector T cells
T cells acquire cutaneous homing receptors
Elicitation Phase (on re-exposure):
T cells migrate to skin
Recognise antigen and release inflammatory cytokines
Inflammatory response at site of contact
Sensitisation can take days to years depending on allergen strength
Irritant Contact Dermatitis:
Non-specific inflammatory reaction (no immune memory)
Triggered by acids, solvents, soaps, plants, chronic moisture (urine/saliva)
Acute ICD: Immediate skin damage from strong irritants, burning/stinging
Chronic ICD: Requires repeated exposure to milder irritants, presents with pruritus (itch)
Patients
Allergic Contact Dermatitis:
Caused by the body’s immune system reacting to an allergen
Most common allergen: Nickel sulphate
Two stages:
Sensitisation:
Body first exposed to the allergen
Cells capture allergen and carry it to lymph nodes
Immune cells (T cells) learn to recognise the allergen and multiply
Allergic Reaction (after re-exposure):
T cells move to the skin and cause inflammation at contact site
This immune memory means reactions can occur long after first exposure
Irritant Contact Dermatitis:
Caused by direct skin damage from irritating substances
Common irritants: chemicals, soaps, plants, moisture (urine, saliva)
Short-term exposure (strong irritants) can cause pain, burning, redness
Long-term exposure (weaker irritants) causes itchy, inflamed skin over time [4]
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Females are more likely to suffer from irritant dermatitis due to exposure to jewellery and fragrances
History of atopic dermatitis
Occupation with high levels of exposure to irritants [6]
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Painful in irritant contact dermatitis
Erythema (redness)
Scaling skin
Swelling (oedema)
Crusting
Blistering
Itchiness [4]
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Occupational history of exposure
History of atopic dermatitis
Previous episodes of similar dermatitis
Referral to a dermatologist
Patch test
Potentially triggering substances are attached to an area of the body using tape
Can be attached to places like the upper arm, the back or the forearm.
2 days later, the patches are removed and assessed to note any reactions.
Can be accessed 2 days post initial investigation as atopic dermatitis reactions can appear later [5]
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Erythema multiforme (an allergic reaction to medicine/infection)
Uriticarial (relating to itchiness) papular plaques (pattern of plaque formation)
Lichen planus (itchy rash)
Pemphigoid (blistering, and itchiness)
Granulomatous (cell pattern that appears after cell injury)
Purpuric petechial reactions (purple, small non raised patches) [6]
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Students
Avoid contact with the irritant or allergen
Topical treatment includes cool compresses (saline or Burow solution) and corticosteroids.
Patients with mild to moderate acute contact dermatitis are given mid- to high-potency topical corticosteroid
Triamcinolone
Betamethasone valerate cream
Oral corticosteroids can be used for severe blistering or long-term presentation
Prednisolone
Systemic antihistamines
Hydroxyzine
Diphenhydramine help relieve pruritus
Wet-to-dry dressings can elevate oozing blisters.
Can also dry skin and aid the healing process.
Patients
Avoid contact with the irritant or allergen
Cool compress, which can be applied to the skin and steroids (to reduce inflammation).
Patients with mild to moderate short-term contact dermatitis are given mid-high effective steroids that can be applied to the skin
Triamcinolone
Betamethasone valerate cream
Oral steroids can be used for severe blistering or long-term presentations
Prednisolone
Antihistamines that treat itchiness, and other allergic symptoms
Hydroxyzine
Diphenhydramine to help relieve itchiness
Wet-to-dry dressings (dressing used to remove dead skin from a wound by wetting the dressing, placing on affected skin and drying. Then removing the dressing which removes the dead skin).
This can alleviate oozing blisters. Can also dry skin and aid the healing process. [4]
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Post- inflammatory hyperpigmentation
Bacterial infection from broken skin due to dermatitis (staphylococcus or streptococcus bacteria)
Impetigo [7,8]
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Direct contact is necessary for contact dermatitis
Soft, 100% cotton is the ideal fabric to wear for contact dermatitis
Gloves protect you against all allergens [9]
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How can I find out what is causing my condition?
How can I protect myself against allergens/ irritants?
What can I do to prevent complications of contact dermatitis?
Is contact dermatitis infectious?
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British Association of Dermatologists
British Skin Foundation
Changing Faces Charity
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[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3276771/
[2] https://jamanetwork.com/journals/jamadermatology/fullarticle/2775575#:~:text=Allergic
[3] https://cks.nice.org.uk/topics/dermatitis-contact/background-information/prevalence/
[5] https://www.nhs.uk/conditions/contact-dermatitis/causes/
[6] https://www.ncbi.nlm.nih.gov/books/NBK459230/#:~:text=Risk
[7] https://ada.com/conditions/contact-dermatitis/
[8] https://www.verywellhealth.com/contact-dermatitis-symptoms-4685650
Source: VisualDx and Skinsight
Contact Dermatitis
Redness and dryness on the inside of the knee
Source: Mind The Gap
Contact Dermatitis
Dermatitis (eczema) is seen on the stomach with redness and white patches
Source: American Academy of Dermatology- National Library of Dermatology
Contact Dermatitis
Subtle redness and grey patches in darker skin tones
Source: DermNetNZ.org
Contact Dermatitis
Contact dermatitis caused by allergens on the arms
Source: DermNetNZ.org
Contact Dermatitis
Allergen causing dermatitis affecting the foot
Source: DermNetNZ.org
Contact Dermatitis
Allergic dermatitis with redness and brown plaques
Source: American College of Allergy, Asthma & Immunology
Contact Dermatitis
Brown plaque formed with follicular lesions due to nickel contact dermatitis
Source: DermNetNZ.org
Contact Dermatitis
Contact dermatitis of the arms with a border and redness
Source: Mind The Gap
Contact Dermatitis
White and grey plaques/ patches on the skin