VOL: 97, ISSUE: 35, PAGE NO: 59
JUSTINE RATCLIFFE, RN, BA, is head of specialty, dermatology, Royal Bolton Hospital
Contact dermatitis occurs in 1.4-5.4% of the population (Williams, 1997), and allergies to topical medicaments, including wound care products, account for 20- 30% of all cases of allergic contact dermatitis (Stone and Powell, 2000; Rook et al, 1998). People with chronic wounds that are occluded by dressings and bandages appear to be most at risk of developing an adverse reaction to topical medicaments and wound care products (Cullum and Roe, 1995; Wilson et al, 1991), but anybody can be affected.
The presence of an adverse reaction has implications for future management of the wound and can have a detrimental effect on the healing process, if left untreated. An awareness of possible reactions to wound care products is therefore essential.
Clarification of terms
Eczema and dermatitis are synonymous, and the terms are often used interchangeably. In this article eczema will be used to refer to endogenous varieties of the condition - for example, atopic eczema, varicose eczema and discoid eczema; dermatitis will be used when the condition is caused by external factors - for example, contact dermatitis.
It is possible to have endogenous and exogenous eczema at the same time. For example, a person with varicose eczema can acquire a superimposed contact dermatitis.
Wound care products are external agents and can cause a contact dermatitis. This is a different process to reactions that are caused by systemic medications. Contact dermatitis can be further subdivided into irritant contact dermatitis (ICD) and allergic contact dermatitis (ACD), depending on the relevant pathophysiology and aetiology.
Irritant contact dermatitis
Irritant contact dermatitis is an inflammatory reaction caused by direct physical or chemical damage to the skin. It accounts for the majority of all cases of contact dermatitis and does not involve an immunological response (Rook et al, 1998).
Almost anyone can develop ICD. For example, most people will react to the repeated application and removal of adhesive tape to and from the skin. How soon the reaction occurs depends on the agent and the individual. Antiseptics can be very irritant and can cause a reaction on the first exposure.
People with sensitive skin and individuals with pre-existing eczema are more prone to ICD, and elderly people are at increased risk, as their skin tends to be drier and less able to compensate for the damage (Rook et al, 1998). Environmental factors, such as occlusion, may increase the potency and absorption of the irritant, which intensifies the damage (Rook et al, 1998).
Agents that can cause ICD in wounds include adhesive tapes, antiseptics, detergents, elastic bandages and wound exudate that has come into contact with surrounding skin. Clinical presentation will depend on whether the reaction is acute or chronic. For example, an acute reaction can develop after a single exposure and is, in effect, a chemical burn. Examples of very strong irritants in this instance include wound exudate and antiseptics. The resultant reaction is erythematous and well demarcated, with blistering in severe cases.
A chronic reaction takes longer to develop and is the result of gradual damage to the skin over a prolonged period of time by weak irritants, such as diluted cleansing products. This reaction may not be as obvious as acute ICD; blistering is rarely seen and the skin may simply appear thickened. This is called lichenification and is a protective mechanism of the skin (Bysshe, 1996).
Irritant reactions always occur at the point of contact, so the causative agent is often easy to identify. However, the clinical presentation can be similar to that of ACD, and it may be difficult to distinguish between the two.
A detailed patient history, clinical examination and a thorough review of past and present treatment regimes is required in all cases. There are no diagnostic tests available to confirm or exclude ICD, as it is impossible to simulate the wound environment in test conditions. If there is any uncertainty whether the reaction is ICD or ACD then patch testing can be carried out to exclude the latter.
Once the reaction has been identified as ICD the causative agent must be removed to allow the skin time to recover. There are a number of actions that can be taken to aid recovery and prevent further damage:
- If wound exudate is a problem, protect the surrounding skin with zinc paste. Mixing the paste with 50:50 white soft paraffin and liquid paraffin will aid application and removal (Shankar and Mortimer, 2001);
- If bandages are causing damage by friction, apply a layer of cotton tubular gauze under them;
- Do not use adhesive tapes directly on the skin to secure dressings;
- Avoid antiseptics if possible. If it is necessary to clean the wound, use tap water or saline.
If the reaction fails to respond or gets worse the possibility that it may be ACD should be reconsidered.
Allergic contact dermatitis
The function of the skin is to protect the body from harmful substances and dehydration (Hughes and van Onelsen, 2001). However, its barrier function can fail and people can become allergic to something they are in contact with on their skin. Why some react and not others is not fully understood. However, broken skin, if covered by occlusive dressings and exposed to a number of topical preparations over a period of time, is at a high risk of developing ACD - for example, people with leg ulcers, burns and pressure sores (Rycroft et al, 1995).
People with leg ulcers are particularly liable to develop ACD. Leg ulcers are often chronic wounds that necessitate the use of a variety of preparations, including known sensitisers such as topical steroids and topical antibiotics, applied over a period of time. Furthermore, venous eczema can often be found around the ulcer, and this compromises the barrier function of the skin and further increases the absorption of allergens into the system. Also contributing to the problem is the fact that the skin is frequently occluded by bandages as part of the treatment regimen. All of the above factors contribute to the development of ACD.
Studies have shown that between 50- 81% of people with leg ulcers who have been tested for ACD have been found to be experiencing this (Cameron, 1995; Wilson et al, 1991; Zaki et al, 1994). This may not represent all leg ulcers, as only chronic, problematic or those strongly suspected of having ACD are patch-tested.
ACD is a type IV immunological response, which means that it is an acquired, delayed cell-mediated reaction to a sensitising substance (Marks et al, 1997). For an individual to become sensitised repeated exposure over a period of time is required. The length of time for sensitisation to occur depends on the substance and the individual.
When sensitised individuals come into contact with a substance they are allergic to and it is absorbed into the body it binds to specific protein markers on the Langerhans cells. These then migrate along the lymph channels to the lymph nodes where they are presented to the T-cell lymphocytes. Recognition occurs and the lymphocytes release substances that stimulate mast cell degranulation. This results in an inflammatory reaction on the skin at the original point of exposure. However, as the Langerhans cells circulate throughout the body a reaction may take place elsewhere on the body as long as direct contact with the skin has been made (English, 1999).
The whole process from exposure to reaction may take up to 96 hours, which is why it is referred to as a delayed cell-mediated reaction.
Acute ACD is characterised by erythema, vesicles, oedema, crusting and pruritus. The reaction usually develops according to the shape and size of the dressing or topical treatment that the person is allergic to, with ill-defined edges. During an acute episode the eczematous changes may be observed on distant parts of the body. This is known as secondary spread.
Medicament sensitisation should be suspected if:
- There are eczematous changes around the wound or where topical medicaments and dressings have been used;
- The wound fails to respond to treatment when there are no other contraindicating factors;
- Recurrent eczematous changes persist around the wound with only a short period of improvement from topical steroids (Stone et al, 2000; Wilkinson, 1999).
Before any investigations a detailed assessment is required, taking into account the patient’s history and a clinical examination. The only diagnostic tool available to confirm or exclude ACD is patch-testing.
If ACD is suspected, a referral should be made to the dermatology department where patch-testing can be carried out. This is done over a 96-hour period to allow time for the cell-mediated reaction to develop. On day one the patches are applied, they are removed after 48 hours and the skin is monitored for any sign of reaction. Final monitoring of the patch tests is repeated after a further 48 hours.
Patch-testing involves an established procedure. A number of pieces of tape or patches are applied to the back on the first visit. Each patch is made of a hypoallergenic, acrylic-based tape. On each patch are mounted five or 10 aluminium discs, 8mm in diameter, and each of these discs will hold one allergen. The allergens are commercially available and already diluted to a specific concentration in petrolatum or water.
The concentration is important; if it is too high it will induce an irritant reaction, but if it is too weak an allergic reaction will not be produced. The allergens tend to be grouped in series or batteries, and the series applied will depend on the patient’s problem. All patients are tested to the standard series (Diagram 1). This is a general series consisting of the allergens that most frequently cause allergic reactions - for example nickel, perfume, preservatives and neomycin. Other series that may be tested for people with a suspected medicament allergy include the medicament, steroid and rubber series.
Patients will be informed to bring along their own topical medicaments so that they can be tested as well.
Before patch-testing the nurse will assess the patient to see if it is possible to test. Medical advice is sought if any of the following is identified:
- A deep sun tan - a recently acquired sun tan on the back may suppress mild allergic reactions (Rook et al, 1998; Rycroft, 1995);
- An eczematous back - patch-testing may cause a flare of the eczema, the results may not be perceivable and the risk of false positives is higher (Rietschell and Fowler, 1995);
- The patient is taking oral steroids - a dose less than 20-30mg per day is acceptable (Marks and Deleo et al, 1997);
- The patient is on immunosuppressants - for example, cyclosporin or azothioprine may suppress a reaction (Rycroft et al, 1995).
If it is suitable to proceed then the patches are applied to the back, which provides a large surface area. The patches are applied in a methodical manner, starting at the top left hand side and working across to the right hand side. The spine is avoided to minimise the risk of pressure damage. The adult back can usually accommodate approximately 80 allergens in two rows of four. Children need to be assessed individually, as the size of their back will dictate the number of allergens that may be applied.
After the patches are applied a skin marker is used to highlight the side of each disc containing an allergen. All the discs are numbered and the sequence along with a map of the back is documented (Diagram 1).
After 48 hours the patches are removed and, once the skin has settled down, usually 30 minutes later, the back is inspected for any reactions. One of two reactions may be observed - an allergic reaction or an irritant reaction. The severity and type of reaction is scored using the International Contact Dermatitis Research Group (ICDRG) scale:
- ’+ A doubtful reaction: faint erythema only;
- + Weak positive: erythema, infiltration and possible papules;
- ++ Strong positive: erythema, infiltration, papules and vesicles;
- +++ Extreme positive: intense erythema and infiltration and coalescing vesicles.
An irritant reaction is erythematous and flat with well demarcated edges that do not extend beyond the margins of the disc. Pustules, bullae and necrosis may be seen. An irritant reaction is either due to the allergen being applied at too high a concentration or the patient’s susceptibility; people with atopic eczema are more prone to irritant reactions.
After 96 hours a final reading is done. This is the optimum time for picking up allergic reactions. Approximately 30% of reactions which appear between the 48- and 96-hour reading and any irritant reactions will be fading. At this stage the dermatologist makes the final diagnosis and informs the patient.
Management of ACD
Once people have been diagnosed as having an allergic reaction to a topical agent it is important that they should avoid it. At my place of work all patients are informed of the allergy and given written information outlining what it is and the type of products it is found in. Patients are rarely given a list of individual products that are safe or unsafe to use, as companies often change their formulations; it is safer to encourage the patient to read the product labels.
The ingredient list on product labels will have two headings, covering the active ingredients and the excipients. The active ingredients are the drugs and the excipients include the vehicles, preservatives and emulsifiers necessary to make up the preparation. Both lists can be significant.
Community nurses and other health care professionals involved in the individual’s care are informed of the diagnosis to maintain continuity. Residual eczematous changes caused by the allergen should be treated with a topical steroid preparation, preferably an ointment, to reduce the inflammation. Bland emollients will re-hydrate the skin and improve patient comfort.
Recommendations for wound care practice
- Keep topical treatments bland;
- Use ointments instead of creams;
- Limit the use of topical antibiotics to a two-week period only;
- Do not keep changing treatments.