Hi Alpha_Beta, and welcome to the forum!
Unfortunatey, you are the first member I am aware of that shares about allergic reaction to sperm stains, even when clothes or sheets have been washed. What is common to all member is reaction after ejaculation, which may be allergic, neurologic, immunologic, or a mix of these factors and others.
Maybe by reading your post, other members will share a common experience.
In the mean time, you could do some testing, like when you have a piece of clothing that is stained, you could try washing it in very warm water, with soap, and then see after if it still causes you allergic reaction. Very hot water will break molecular structures of organic compounds in the sperm stains, so after they are reduced to simpler elements, and that proteins and fats have been degraded, the potential for allergy is greatly reduced.