How to do a 2 part Patch Test – L’Oreal Excellence

This is a how to do a patch test using both the colourant and developer. It is advised by Allergy UK  that if you are using a 2 part hair dye – then you should perform a skin allergy patch test using the same formulation as you would on your hair.

A small disclaimer – The photos used are of my arm. At the time I was taking some prescribed medication for migraines, hayfever nasal spray and over the counter antihistamines Zirtek. I do get eczema, I have no tattoos, I have never smoked and I have never had any henna tattoos.

Here is the skin allergy patch test. The patch test itself took no more that a few minutes to do and the drying time was between 30 minutes and 1 hour.
This is the method I would use for any hair dye, as this is the same mixture as would be applied to my head and hair.

My inner elbow before and the hair dye colourant and developer containers.


containers-2part - MixEz

First the colourant tube- undo the lid and pierce the foil seal with the pointed section on the top of the lid. There is a bit of yellow coloured liquid which comes out first. This is not what you use for the patch test – this creates an air tight seal and prevents any oxygen getting to the colourant and the colourant from not working.

Squeeze a small amount of the creamy yellow creme into a small container. On the back of the tube there will be a ratio this tube had 1:1.5.


Then undo the top of the bottle of the developer and pour approximately the same amount of developer, a white liquid, into the container and then a half again to get the approximate ratio 1:1.5.


Mix together carefully and then apply a 10p size onto the inner elbow or behind the ear with a cotton bud.



As there is a chemical reaction taking place (as there would be on the hair) the mixture will go dark which shows the PPD is oxidising.


I used far too much (tried to use my left hand) but it is easily cleaned up after staying on the skin for 45minutes. I also moved by arm around which meant the mixture travelled slightly.


Here is my arm after I cleaned off the residue with a damp cotton bud.

1hr-cleaned-up-2part - MixEz

This is my arm after 48 hours, completely clear of anything.


All the photos I took for my 48hour patch tests are on my twitter account.

If there is any sign of redness, welts, hives, soreness – contact your doctor immediately for medical advice.

This entry was posted in At home, Hair Dye, L'Oreal, Patch Testing, Permanent and tagged , , , , , . Bookmark the permalink.

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