Thanks for the query,
As you have psoriasis
, your skin is highly sensative.
Any product like soap or any chemical can irritate you.
Folds of skin are more prone to collect these chemicals and develop allergy
You may need treatment with steroids
Please meet a dermatologist
for final diagnosis and treatment
Let me know if you have any other doubt.
you can ask a direct question to me on this forum, following the below link.
Wishing you a good health.