Red itchy bumps on vagina hood..

It is common for people to be sensitive to detergents and certain metals. Sometimes it is the chemicals added to give the soap a 'fresh scent' that can cause such a reaction. As a possible solution, you could try switching to a detergent with no scent. You could go even further and purchase some soap from one of those multi-level marketing companies like Amway or Melaleuca. This isn't a sales pitch. To be honest, I find their soap does not do quite as good a job as regular storebought. However, it does get clothes clean. If you don't already, wear cotton underwear that you find comfortable. It lets your skin breathe, which could help prevent the problem even further.

Now for the sex.
The skin is getting bumped, wet, and there is alot of friction going on during sex. That's just the nature of it. With any luck, your skin is under less stress overall by using alternative soap and wearing cotton. It is possible that the affected area will be less prone to break out after sex.

If the problem persists, or you notice it getting worse, don't mess around. Get to the doctor and have it looked at.

if you are sensitive to detergents use less a lot less most people use far more than they need . try washing your clothing without soap it will still suds up because household laundry washers only have 1 or 2 rinses try a commercial washer like a wascomat in a laundromat they have 5 changes of water 3 rinses . again do not use more than 1/4 cup of any soap and you will see a diff. good luck