What to do if allergic to fabric softener?

Avoid. An allergy to fabric softener results in a skin rash wherever your skin comes in contact with fabric that is "contaminated" by fabric softener. The only effective treatment is steroids - topical of mild, and oral if the rash is severe. However, it is far better to avoid the contact in the first place. Unfortunately, there is nothing you can do to avoid the rash other than to avoid all contact.