Patch recommended test concentrations

The proper test concentration and the best vehicle for all the chemical substances should be estimated carefully on the basis of the information on toxicity and the composition of the material available. In addition, one should check which of the individual chemical components are available from the suppliers as patch-test substances, because one may rely on their choice of vehicle and concentration and these substances, if available, should be included in the test battery of the patient. It is helpful to use selected test series related to a specific type of product aimed to be tested, e.g., metal-working series for metal-working fluids. Several reports provide useful information on the concentrations and vehicles to be used (Fregert 1981 De Groot 1994 Guin 1995 Niklasson 1995 Rietschel and Fowler 1995). The test concentration for the chemical substance should not exceed the previously recommended test concentration for any of the components. This may, however, lead to the risk of the over dilution of potential allergens, especially when the responsible ingredient is present in a low concentration or appears as a contaminant in the product. 

The formaldehyde concentration in patch-testing, which has been lowered to 1% in the standard series in recent years, has been studied in a comparison of concentrations of 1% and 2% in 3734 consecutively patch-tested patients (11). Since there was no significant difference between 1 and 2% formaldehyde with respect to the frequency of positive patch test reactions, while there were more irritant reactions with 2%, a 1% patch test concentration can still be recommended. 

It is recommended that PVP-I not be used on young children (neonates and babies) (Wissenschaftlicher 1980). Iodide, which is spoiled per operationem between skin and electrocoagulation electrodes, could result in serious burning wounds. Patch-test concentrations are as is and 10% pet. Allergic reactions are considered rare. 

Andersen KE, Rycroft RJ (1991) Recommended patch test concentrations for preservatives, biocides and antimicrobials. Contact Dermatitis 25 1-18... 

In general, a patch test concentration of 2% in petrolatum is recommended for the methacrylated monomers, and 0.1% in petrolatum for the acrylated monomers to avoid patch-test sensitization (Kanerva et al. 1988). 

Emmett EA, Ng SK, Levy MA, Moss JN, Morici IJ (1989) The irritancy and allergenity of 2-n-octyl-4-isothiazolin-3-one (Skane M-8 ), with recommendations for patch test concentration. Contact Dermatitis 20 21-26 Engel HO, Calnan CD (1963) Chromate dermatitis from paint. Br J Ind Med 20 192-198... 

Ethanol, methyl ethyl ketone and acetone are recommended vehicles for patch tests of materials and products brought to the physician by patients, indicating that vast experience has demonstrated these solvents to be only marginal irritants (Wahlberg 1995b). Propylene glycol has irritant properties under occlusion, and the optimal test concentration and vehicles are not yet settled (Wahlberg 1994). 

Allergic contact dermatitis occurs most commonly from nickel-containing objects, plants (such as Rhus)y rubber, adhesives, or dyes in athletic tape, gear, or running shoes, and topical medicaments. Reactions are induced or elicited by the athlete s perspiration, which leaches the chemical allergens from their gear (Cronin 1980). Table 6 lists common contact allergens in the athlete and their recommended patch-test concentrations (Marks and DeLeo 1997). 

Compound that may cause persistent light reactions Compound that may cause phototoxic reactions Recommended patch test concentration and vehicle Uncertain mechanism type contact urticaria (structural formula described in Table 62.4)... 

In concentrations greater than 10%, propylene glycol may act as an irritant in some patients those with eczematous dermatitis may be more sensitive. Allergic contact dermatitis occurs with propylene glycol, and a 4% aqueous propylene glycol solution is recommended for the purpose of patch testing. 

Brown and Kaplan presented a more complex solution of phenol (at varying concentrations between 60% and 95%) mixed with saponified cresol in oil at concentrations of up to 10%. The application technique included a patch test behind the ear. This test made it possible to assess the necrotic effect of the solution on the patient. If the necrosis was too severe, the test was repeated with increasing concentrations of oil until the right solution for the patient was found. They recommended applying the solution area by area, leaving 2 hours between applications. The peel took 2 days to complete. 

Table 2. Recommended vehicles and concentrations in dilution series for patch testing industrial chemicals...

Recommended Concentrations and Vehicles for Patch Testing the Patients Own Industrial Chemicals... 

Patients may also be patch tested with a swatch of the suspected fabric, applied dry and/or wet. If the patient is patch-test positive, this identifies the fabric that contains the offending chemical. However, a negative does not rule out the possibility that the fabric does contain the allergen. The conditions may not permit the transfer of the offending substance or may not permit transfer at sufficient concentrations to elicit a response, and without that essential transfer step, a positive will not occur. At one time, it was recommended that the fabric should be steamed prior to application, but that recommendation has been withdrawn (Foussereau 1992). 

Patch testing can also be done with an extract of tulip bulb (the Apeldoorn variety is suitable). This is done by shaking fresh bulb material in 80% acetone (in water) for 90 min, evaporating it dry and resuspending it in a 1% concentration in alcohol [109]. The bulb surface is also satisfactory after the brown outside layer is removed. Controls are recommended. One patient developed depigmentation from testing with Alstroemeria [112]. 

Steps in batik processing Irritant Allergen Concentration (%) recommended for patch testing [13, 14] Comments... 

Direct skin contact of the veterinarian with animal medications has probably diminished since the 1970s in many countries. Antibiotics (and other medications) used in veterinary medicine and also animal feed are mainly the same as in human medicine, e.g., penicillins, cephalosporins, macrolides, tetracyclines, quinol-ones, sulfas, trimethoprim, antifungals. In addition, other substances have been used in animals only, e.g., penethamate, tylosin, spiramycin, furazolidone. Many antimicrobials are contact sensitizers and may cause contact dermatitis at low concentrations. No routine series for patch testing can be recommended because of the risk of active sensitization. Patch testing should be done with the particular medications with which the veterinarian has been in contact directly or via fodder. Contact urticaria from several antibiotics and disinfectants has also been reported (Hannuksela 1997b Kanerva 1997). 

This was the third similar case seen by the author. In view of the serious generalized reaction observed, the author recommends the use of low concentrations in patch testing, especially if sensitivity to other mercurials has previously been detected. 

---