Contact dermatitis in the older patient: what are the challenges?

Contact dermatitis is inflammation of the skin, which results in a collection of clinical findings that occur in response to an external stimulus acting as either an allergen or an irritant.

In recent decades life expectancy has increased consistently with a corresponding increase in the global population of older adults. This is due to improved nutrition, sanitation, medical advances, health care, education and economies. It is predicted by the year 2050, 20% of the global population will compromise of adults over 60 years. In developed countries life expectancy is currently 78 years and this is expected to increase to 83 years by 2050.¹

Contact dermatitis can be further separated into allergic or irritant contact dermatitis.²Allergic Contact Dermatitis (ACD) is a delayed hypersensitivity T-cell mediated inflammatory reaction which occurs at the site of challenge with a contact allergen in sensitised people.³ The overall rate of positive patch test has been found to be significantly decreased in a large series of 1,444 patients over 65 years as compared with a control group. There was however an increased number of positive reactions to particular allergens.

This could possibly reflect previous exposures when certain substances were more common in the workplace and also the presence of some of the substances as constituents of topical medications that the older patient will be more likely to use.4 The most frequent allergens in the older population are nickel sulphate and topical medicament-related agents, including fragrance mix (10-12.9%), Balsam of Peru (8%), neomycin (7-8.8%), gentamicin (6.6%), and lanolin – detected by wool alcohols and Amerchol L-101 [1-4.5%].^2,3

Irritant Contact Dermatitis (ICD) is a nonspecific inflammatory response that occurs after damage to the skin. ICD does not require prior sensitisation and can occur in any individual exposed to an irritant for a sufficient duration and concentration.²

There is a decreased reactivity to irritants in older patients over the age of 65 years. This trend has been seen with chemical irritants such as sodium lauryl sulphate, histamine, dimethyl sulfoxide (DMSO), compound 48/80, chloroform-methanol, lactic acid, and ethyl nicotinate.⁵ It can sometimes be difficult to distinguish allergic and irritant contact dermatitis clinically, particularly in their chronic forms.

Acute ICD is more likely to be associated with an onset of reaction within 48 hours, burning and stinging sensations, with the rash only affecting areas of skin exposed to the irritant and resolution occurring within 96 hours of removal of the irritant. Acute ACD may present with pruritus in areas directly or indirectly in contact with the allergen, after a delay of many hours to several days and resolution can take many days, with or without treatment.²

Changes in ageing skin and immune mechanism

With increasing age some key functions of the skin are impaired. This includes cell replacement, barrier function, chemical clearance, mechanical protection, immune responsiveness, wound healing, thermoregulation, DNA repair, sweat and sebum production and Vitamin D production.⁶

Due to impaired epidermal barrier function, delayed recovery after barrier damage, and decreased epidermal lipid synthesis, chronologically aged skin may be more susceptible to contact dermatitis.⁷ Xerosis is characterised by pruritic, dry, cracked and fissured skin with scaling. This results in epidermal water loss, skin splitting and deep cracks and bleeding fissures. Scratching and rubbing movements generate excoriations, an inflammatory response and lichen simplex chronicus. Consequently, this may lead to an increased risk of allergic and irritant contact dermatitis and infection, as environmental allergens and pathogens can more easily penetrate the skin.⁶ Aged skin also requires more time for regeneration.⁸

Impaired epidermal barrier function increases the concentration of Langerhans cells and cytokine production.⁹ However, the concentration of epidermal Langerhans cells and the production of cytokines decrease with age and also photodamage. Therefore, in the older population these factors make allergic contact dermatitis less likely and, if present, less inflammatory.¹⁰

Photodamage also adds to the delay in recovery time in aged skin. However, increasing age leads to a greater number of exposures and longer exposures to possible sensitising agents and therefore an increased risk of allergic contact dermatitis.¹¹

Patch testing

A detailed history and pattern of distribution is helpful for diagnosis of contact dermatitis. It is important to do a thorough investigation of the new substances the patient is exposed to as well as tracking down substances, which the patient has been using for decades.³ This can be challenging in older patients with dementia. Patch testing is the gold standard assessment for ACD and uses a series of allergens to look for common possible sensitisers.^2,12

It can be challenging to apply patches on older patients with spinal deformities such as kyphosis. Furthermore, patients living in nursing homes or with mobility difficulties may find it difficult to attend a dermatology clinic three times in one week.

It is important to assess whether patch test reactions are of current, past or debatable relevance, as studies have shown a 37% prevalence of patch test reactivity in an older population without any evidence of dermatitis¹¹ and that patch test reactivity can persist for at least 10 years.¹³ Patch testing in older patients has also been found to have a slower onset of reactivity, less intense reaction and prolonged recovery compared to the younger population. Therefore, in this population it is important to consider an additional reading after seven days and the interpretation of weak reactions as true positives.^4,9,15

Comorbidities

Patient’s comorbidities and pre-existing disease states and treatments make the older population more prone to develop contact dermatitis. This includes end-stage renal disease, diabetes, nutritional deficiencies, thyroid disease, neurological disease, medications, HIV, malignancies, functional limitations and personal habits.^6,15 In addition, there are more obscure exposures in the older patient like benzyl alcohol in hearing aid impression material,16 acrylic monomer in a denture,¹⁷ coronary stent materials,¹⁸) and implant materials for total hip replacements.^19,20

Both irritant and allergic dermatitis are predisposed by urinary/faecal incontinence and ostomies from urinary and gastrointestinal procedures which disturb the natural skin barrier.^21,22 Older patients are more susceptible to moisture-associated skin disease as cell replacement is decreasing which results in a thinner dermis and a defective and delayed wound healing process.²³

Due to prolonged exposure to faeces or urine, incontinence-associated dermatitis (IAD) is an increasing concern especially in older patients with long term incontinence, a high Body Mass Index (BMI) or type 2 diabetes.²⁴ Prolonged skin exposure to urine and faeces combined with moisture, alterations in pH, friction, ammonia and secondary infection are the external provoking factors in IAD.²³

Allergic contact dermatitis is a common cause of vulval pruritus and vulval pain. A retrospective study looking at allergic contact dermatitis of the vulva, showed that there was a higher rate of relevant results in females over 70 years compared to those younger than 70 years.²⁵

In older patients, contact dermatitis is more common in the lower extremities compared with the face and hands.² Approximately 2% of the population aged older than 65 years are affected by chronic leg ulcers. These patients have a high risk of contact allergy as many topical medications are used and their sensitisation increases with the duration of the chronic leg ulcers.³

Treatment of contact dermatitis

The first line therapy for contact dermatitis is to identify and avoid appropriate irritants and allergens. It is often difficult to distinguish between irritant and allergic contact dermatitis and sometimes there is an overlap of both conditions.² Patients should be given detailed information on avoidance therapy once relevant allergens and irritants are determined.

Patient information leaflets and product labelling designed to facilitate allergen avoidance in patients with allergies may be challenging for older patients with reduced vision. There may also be a difficulty in communication due to deafness or reduced cognition that could cause problems assessing exposures and also giving meaningful advice about results. In addition, applying topical treatments can be challenging for some older patients who are bed bound and have spinal or hand deformities.

Can we reduce some of the contact dermatitis challenges?

In January 2000, the Nickel Directive became law in the Europe Union specifically for the prevention of sensitisation and stimulation of nickel dermatitis. As a result of this law, it has been shown that items intended for direct and prolonged contact with the skin, such as jewellery and clothing containing nickel content and nickel release, has decreased compared to levels pre-legalisation in 1999.²⁶ This suggests that the risk of sensitisation and subsequent ACD could be reduced by further implementation of these laws.² However, it may not result in very great improvements for older patients because sensitivity may result from previous exposure.

Conclusion

Contact dermatitis is a significant cause of skin disease in the older patient and with increasing life expectancy it is yet to become an even larger health problem. With increasing age there is reduced skin barrier function but also a reduced prevalence of ICD, which is normally increased by reduced barrier function. On the other hand, declining immunity decreases the tendency of sensitisation in the older patient. The incidence of contact allergy to certain allergens increases with age. But overall it seems likely that the rate of positive patch tests decreases. Contact dermatitis in the older patient is challenging due to this interplay of both intrinsic and extrinsic factors.

In addition, contact dermatitis in the older patient has a significant societal, economic, psychological and physical impact and can lead to depression, lack of sleep and discomfort in the older patient if they are not treated.

Both forms of contact dermatitis need a thorough history, full skin examination and comprehensive patch testing for diagnosis. Despite these measures, it can still be challenging to distinguish between irritant and allergic contact dermatitis, perform patch testing and treat contact dermatitis in older patients.

Sukhjit Dhariwal, ST3 Dermatology training, Warwick Hospital

This article was the winning entry for the British Society for Geriatric Dermatology, Kligman Essay Competition in 2019.

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