In this CCC, we will cover contact dermatitis and also look specifically at nappy rash in children.
Contact dermatitis is either an allergic or irritant skin reaction. We can classify them as either of the 2 types:
- Irritant contact dermatitis (ICD) - this is caused by direct toxicity to the skin without any prior sensitisation required. It can occur in anyone who comes into contact with an irritant of sufficient concentration for a sufficient amount of time. The severity of the disease corresponds with these 2 factors as well. It can also range from acute (single exposure) → chronic (repeated exposure). Repeated exposure can disrupt the epidermal barrier and lead to transepidermal water loss. Typical irritants include:
- Metals
- Solvents
- Detergents
- Weak acids and alkalis
- Cement - it is alkaline and may cause ICD but the presence of dichromates in it also may cause ACD.
- Allergic contact dermatitis (ACD) - this is a type 4 hypersensitivity reaction that does require prior sensitisation. It is relatively rarer compared to ICD. It occurs due to allergens which are typically haptens. Haptens are small molecules that cause an immune response when bound to other proteins (hapten-protein complex [HPC]). The HPC enters the epidermis and binds to Langerhans cells within the epidermis. These are the APCs of the integumentary system and they travel to regional lymph nodes to present to CD4+ T-cells which produce a response in 48-96 hours of re-exposure. Common allergens include:
- Poison ivy
- Fragrances
- Metals (nickel for example)
- Jewellery
- Preservatives - especially in cosmetic and hygiene products
- Hair dyes
- Chromates - found in cement and leathers.
- Latex
⚠️ Risk factors
- Occupational exposures - labourers, food-industry workers, machine operators, farmers, healthcare professionals, janitors, dry cleaners, cooks, florists, beauticians and hairdressers.
- Atopic dermatitis (eczema) - increased risk of developing ICD (but not ACD).
😷 Presentation
Presents within minutes-hours of exposure to severe irritants. Mild irritants can take days-weeks to present with ICD.
It most commonly occurs on hands and face and is limited to the site of exposure:
- Erythema
- Burning
- Pustules or acneiform lesions
- Ulceration - may occur with severe irritants.
ACD presents within 24-72 hours of exposure (previously sensitised).
It often affects the dominant hand but anywhere may be affected. Often it can affect the margins of the hairline.
- Erythema
- Pruritus
- Vesicles and bullae
- Uriticaria - with exposure to latex and certain foods.
🔍 Investigations
- Patch testing - allergens are presented onto the skin using a path and this will show inflammation which can be graded on a scale within 2-7 days of application if positive for a specific allergen.
- Repeated open application test (ROAT)/provocative use test (PUT) - the test is performed 2x daily for 1 week and best simulates the contact dermatitis caused by leave-on products (moisturisers, sunscreens and cosmetics).
😷 Management
Of course for both ICD and ACD, the first-line option is to avoid irritants/allergens.
- Emolients should be applied to the affected area in ICD.
- Topical corticosteroids - such as hydrocortisone can be used for ACD.
Nappy rash, also known as diaper dermatitis or napkin dermatitis is an acute inflammatory reaction of the skin in the nappy area. It is a form of irritant contact dermatitis.
It is estimated that nappy rash affects up to 25% of nappy-wearing infants at some point.
Pathophysiology
Friction between the skin and nappy as well as contact between the skin and urine/faeces leads to nappy rash.
The friction and prolonged contact leads to loss of the skin barrier function which leads to an increased skin pH. This decreases the skin’s function to prevent microbial colonisation. This causes pathogenic colonisation and predisposes the baby to secondary infection with bacteria and fungi.
The common microbes that lead secondary infection are:
- Staphylococcus aureus
- Streptococcus spp.
- Candida albicans
⚠️ Risk factors
- Delayed nappy changing
- Irritant soap products and vigorous cleaning
- Poorly absorbent nappies
- Diarrhoea
- Oral antibiotics - this may predispose the baby to candidal colonisation.
- Prematurity - due to the poor barrier function in immature skin.
😷 Presentation
As nappy rash is uncomfortable and itchy, the infant may be distressed.
- Sore, red, inflamed skin in the nappy area - it tends to appear in patches on exposed areas of the skin that come into contact with the nappy. It spares the skin creases as these don’t tend to come in contact with the nappy.
- Red papules - may be present alongside the affected areas of skin.
- Erosions and ulcerations - if the nappy rash is severe and longstanding.
Signs that point towards candidal infection are:
- Rash extending into skin folds
- Larger red macules
- Well demarcated scaly border
- Circular pattern
- Sattelite lesions
🔍 Investigations
It is a clinical diagnosis.
🧰 Management
We can take simple measures to improve skin health and treat the nappy rash within a few days:
- Use highly absorbent nappies
- Change nappy and clean the skin as soon as possible after wetting/soiling - cleaning should be done with water or gentle, alcohol-free products. The area should be dry before replacing the nappy.
- Maximise time without nappy.
💊 We can use pharmacological treatments if secondary infection has occurred:
- Clotrimazole or miconazole - if fungal infection is suspected.
- Fusidic acid or oral flucloxacillin - if bacterial infection is suspected.
- Hydrocortisone 1% cream - if the rash appears inflamed and is causing discomfort.
🚨 Complications
- Seondary infection
- Jacquet’s erosive diaper dermatitis - this is when there are punched out ulcers or erosions with elevated borders.
- Cellulitis