GB2239708A

GB2239708A - Allergy patch testing

Info

Publication number: GB2239708A
Application number: GB8919209A
Authority: GB
Inventors: Sam Shuster; Janet Mclelland
Original assignee: Individual
Current assignee: Individual
Priority date: 1989-08-24
Filing date: 1989-08-24
Publication date: 1991-07-10
Also published as: GB8919209D0

Abstract

Test kits for patch-testing of suspected contact dermatitis comprise patches containing a variety of mixtures of different materials or have at least some patches which contain different concentrations of the same suspected allergen.

Description

AN IMPROVED METHOD FOR PATCH-TESTING This invention relates to an improved method of patch-testing for the detection of chemicals causing contact dermatitis.

Contact dermatitis is a common skin disorder caused by an irritative or allergic response to many different chemicals which come into contact with the skin, e.g. perfumes and preservatives in cosmetics, nickel in jewelry, and dyes in clothing, as well as the many chemicals and products used industrially. The cause can only be suspected on clinical grounds, and confirmation has always to be sought by an investigation known as "patch-testing". Patch-testing is carried out by dermatologists who apply the suspected chemicals to the skin on an absorbent patch or in a small chamber left in contact with the skin for 48 hours under an adhesive, after which the development of an inflammatory reaction indicates that the patient is sensitive to that particular chemical. There are a number of disadvantages with this technique: 1.Because of the large number of chemicals involved, the dermatologist has to carry out many patch-tests. This takes up much patient and clinician time and is costly. It is also difficult when the area of normal skin available for study is limited.

2. Sometimes both patients and doctors are convinced of an allergy to a particular product from circumstantial evidence, yet this cannot be confirmed because patch-tests to its individual constituents are negative.

3. Conversely patients sometimes give a positive reaction to a particular chemical in a patch-test, but this appears not to be relevant in that the patients can continue to use products containing this chemical with impunity.

4. Because of the large numbers of potentially causative chemicals involved, investigation and testing is done by a dermatologist rather than the family doctor.

We have studied these problems and found that by including a number of unrelated potential chemical allergens in the same patch-test, the response to an individual constituent can still be detected. Therefore by using a small group of patches, each containing a mixture of the chemicals conventionally applied in single patch tests, the number of patch-tests required to cover the whole of the potential field is very greatly reduced and the diagnosis is thereby simplified and made less costly.

We have discovered that the reason true allergy may exist to a particular product and yet the conventional patch-tests are negative is because there is an additive response when two or more different chemicals are applied together. Thus we have shown that, although the response to individual patch test constituents may not cause a reaction, when applied in a patch-test as a mixture of the separate constituents the sub-clinical reactions to the separate chemicals will summate to produce a reaction and a consequent dermatitis.

We have also shown that patch test constituents which give a negative reaction by themselves will produce a reaction in the presence of small quantities of other chemicals in concentrations which by themselves produce a mild or no irritation. The use of such mixtures of chemicals also improves the sensitivity of patch-testing.

We have shown that the response to chemicals used in patch-tests is related to the logarithm of the dose applied. We have found this to be the explanation of why patients may give a positive patch-test, yet in practice are totally unaffected by products containing the constituents to which they were found sensitive by patch-testing. In other words, degree of sensitivity is as important as its simple presence and absence. This insight is not novel: what is new is the provision of a package of a minimum of three different concentrations of each patch-test constituent to establish sensitivity of an individual, and therefore allows the doctor to predict the relevance of the patch test reaction to the patient's clinical problem.

The way in which these discoveries will be used in our invention is now described. We will use pre-packed patch-test materials which are readily available. These are standard and consist of a series of absorbent patches on an adhesive strip: the protective cover is peeled and the patches containing test material are applied directly to the skin. Instead of using the conventional single concentration of a single chemical we will use mixtures of unrelated chemicals & series of different concentrations.

Fig. l(a) is a list of commercially available chemicals for patch-testing.

Fig. l(b) is a list of constituents of 27 most frequently used patch-tests which includes the 24 routinely used for confirmation of suspected sensitivities in Europe. Each material is applied separately so that 24 test patches are applied to each patient.

Our invention will provide various mixtures of unrelated chemicals in each patch, which would allow comparable test responses with many fewer patches. Thus for example by using the constituents of 4 conventional patch-tests in each patch, 6 patches can be used instead of 24. Since in patch-testing only about 20% of patients give a positive patch-test response, this simple screening battery of patch-tests would be a great economy both for general practitioners and specialist dermatologists. If, however, 1 of the 6 comes up as a positive reaction, a second series of 4 patches can then be used to define which of the 4 is the responsible antigen. An alternative procedure is to use a larger number of patches, for example 10, in which the materials are incorporated more than once so that the reactivity indicates the specific cause previously identified by 17 conventional patches.

Fig. 2(a) illustrates one such test combination. A patch test response in D & J denotes Nickel and E & I neomycin sensitivities, etc.

Fig. 2(b) gives an example in a patient in whom the new patches each containing mixtures of materials used singly in conventional patches and the single conventional patches were tested to show that our invention gives the same results as conventional testing with fewer patches.

Fig. 3(a) is from our studies illustrating the effect of mixtures of 2 unrelated chemicals showing that the effect is additive when applied together.

Fig. 3(b), also from our studies shows that a response may be negative to one product alone but becomes positive when given in a mixture with others.

In our invention we therefore use a variety of mixtures of chemicals. A number of different mixtures will be provided to cover both the main and less common causes of sensitivity.

Fig. 4 shows that the concentration of applied chemical allergen determines the severity of the response. Based on this finding from our studies, our new patch-test pack will provide a series of concentrations necessary to determine sensitivity to any of the agents currently used in conventional patch-tests.

Fig. 5 illustrates one of our studies of the effect of a chemical allergen applied with and without an irritant showing that the response to the allergen is greater when applied with an irritant and we have shown that patches which are negative become positive if applied with an irritant.

We will provide a series of patches which include allergen with irritant, allergen alone and irritant alone for detection of sensitivity where patch test reactions are negative despite a high degree of clinical suspicion.

These various combinations and concentrations will be so adjusted that they can be used by dermatologists, whose work will be both simplified and made more precise, and also as a simplified pack designed for use by general practitioners who can thereby decide whether the patient requires referral to a dermatologist.

Claims

tSATM.R

We claim that by using our invention of sets of patches containing a variety of mixtures and concentrations of different materials previously used separately that the diagnosis of contact dermatitis will be greatly simplified and made more accurate. The main advantages are that many fewer patches will be used, thus taking up less patient and doctor time and costing less, and that diagnosis will be improved because the tests will reveal reactions which would not be found with conventional testing.

Subsidiary advantages are that the degree of sensitivity of the reaction will be determined so that the relevance of patch testing to the clinical problem will be more secure; furthermore, the simplification introduced by grouping of tests will facilitate the work of the dermatologist and also permit some of the testing to be carried out by the general practitioner without referral for specialist investigation.

Amendments to the claims have been filed as follows CLAIMS: 1. A diagnostic kit for use in the diagnosis of dermatological sensitivity to selected chemical allergens by patch testing, said kit comprising a plurality of patches characterised in that individual patches contain mixtures of different chemical allergens.

2. A kit according to Claim I wherein each of a plurality of different patches contain two allergens.

3. A kit according to Claim 1 wherein each of a plurality of different patches contain three allergens.

4. A kit according to Claim 1 wherein each of a plurality of different patches contain four allergens.

5. A kit according to any preceding claim in which the patches of at least one pair of patches both contain at least one chemical allergen in common.

6. A kit according to Claim 5 in which the patches of a plurality of pairs of patches contain at least one chemical allergen in common.

7. A kit according to any preceding claim wherein said chemical allergens are selected from the allergens listed in the tables appearing in figs l(a), l(b) and (2a).

8. A kit according to Claim 7 wherein at least one patch contains one of the following combinations A-J A Mercapto Quaternium Benzocaine B Germall 115 Carba Chromate C PTBP resin Cobalt PPD Quinoline D Parabens Fragrance mix Thiuram Nickel E Epoxy resin Neomycin MBT F Mercapto Germall 115 PTBP resin Parabens G Quatemium Carba Cobalt Fragrance H Benzocaine PPD Epoxy resin I Chromate Thiuram Neomycin J Quinoline Nickel MBT 10. A kit according to any preceding claim wherein at least one group of patches contains a selected chemical allergan in a plurality of different concentrations.

11. A kit according to any preceding claim wherein a series of absorbent patches are provided on an adhesive strip.

12. A diagnostic kit for use in the diagnosis of dermatological sensitivity to selected chemical allergens by patch testing, said kit comprising a plurality of patches characterised in that at least one group of patches contains a selected chemical allergan in a plurality of different concentrations.

13. A kit according to Claim 12 including patches with at least three different concentrations of patch-test constitutents.

14. A kit according to Claim 12 or Claim 13 including a plurality of patches each containing a mixture of different chemical allergens.

15. A kit according to Claim 14 wherein each of a plurality of different patches contain two allergens.

16. A kit according to Claim 15 wherein each of a plurality of different patches contain three allergens.

17. A kit according to Claim 15 wherein each of a plurality of different patches contain four allergens.

18. A kit according to any of Claims 14 to 17 in which the patches of at least one pair of patches both contain at least one chemical allergen in common.

19. A kit according to Claim 18 in which the patches of a plurality of pairs of patches contain at least one chemical allergen in common.

20. A kit according to any of Claims 12 to 19 wherein said chemical allergens are selected from the allergens listed in the tables appearing in figs l(a), l(b) and (2a).

21. A kit according to Claim 21 wherein at least one patch contains one of the following combinations A-J A Mercapto Quaternium Benzocaine B Germall 115 Carba Chromate C PTBP resin Cobalt PPD Qunnoline D Parabens Fragrance mix Thiuram Nickel E Epoxy resin Neomycin MBT F Mercapto Germall 115 PTBP resin Parabens G Quatemium Carba Cobalt Fragrance H Benzocaide PPD Epoxy resin I Chromate Thiuram Neomycin J Quinoline Nickel MBT 22. A kit according to any of Claims 12 to 21 wherein a series of absorbent patches are provided on an adhesive strip.