On 26/04/2021 10:23, Harry Bloomfield wrote:
For several months now, I have had an ongoing itchy rash on the back of
both hands, close to the area of my thumbs. For quite a while, I have
been racking my brain trying to work out what might be causing it. My
best guess was washing up, but I have always done at least my share of
that. Then I realised the rash appeared when we swapped from Fairy, to
Elbow Grease liquid - as it seemed to be just as good and a little cheaper.

On Thursday in the interests of experimentation, I picked up a 2L bottle
of Fairy and have used that in the days since then (SWMBO is away). The
rash now seems to have almost gone.

OK. Now you need to determine if the allergy is to the detergent or SWMBO.