A Repeated Open Application Test (ROAT) is a provocative use test used to assess the clinical relevance of exposure to an allergen or product identified on patch testing. ROATs are useful when patch testing shows equivocal or doubtful patch reaction, or when there is a negative patch test reaction to a particular allergen or product, but the history is very suggestive of contact allergy.
It can also be beneficial if there is uncertainty about composition of a person’s own product such as whether their own product contains a particular allergen that has been identified on patch testing.
There are also occasions when a patient thinks a particular product has caused them a rash or dermatitis, but patch testing has been negative. ROATs can also be used in this scenario to try and replicate the rash.
What products can be tested?
- Generally only used for leave on products such as cosmetics, moisturisers, perfumes and sunscreens
- It can be used for wash-off products, but real-life use must be simulated i.e. the product needs to be applied and then washed off
How to perform a ROAT
- Apply a product or substance to the inner forearm near the cubital fossa but NOT IN IT (i.e. don’t apply to an area of skin that will be occluded)
- The area of skin should be free of rash when testing begins (otherwise it will be difficult to interpret the ROAT)
- Only a small amount of the substance is needed (about 0.1ml)
- The substance is applied to a 5cm X 5cm area of skin. This area should be marked with a skin marker or tapes, to ensure the product is applied to the exact same area each time it is applied (Figure 1)
- The product should be applied TWICE daily for 7 days (or until a rash/dermatitis develops)
- If still negative, the testing may continue for up to 21 days
- If there is still no rash after this time, the product can be considered safe to use
- On occasion the ROAT may be applied to the face or neck, as this skin is more sensitive
Results
- There are no formal guidelines about reading of results for ROATs. They can be graded as negative, mild, moderate or severe
- Often the first reaction of a positive ROAT is follicular. This may be followed by erythema, papules, infiltration and vesicles
- There is often a reaction seen by day 4 of performing the ROAT
- The ROAT can be ceased when a reaction has developed
Be aware of false negative reactions, which can occur if
- Someone has been using corticosteroids which can dull the strength of the reaction
- The protocol for the ROAT has not adequately been followed
- The area of skin the ROAT has been applied to is different to the skin that the product is designed for, such as eye medicaments. Eye drops or eye medicaments are weak allergens and tape stripping of the skin may be required
Limitations
Performing ROATs can be time consuming and there is often difficulty with compliance, given that the product has to be applied for up to 21 days.
Videos to watch:
