The answer is usually no but there are some exceptions. You must wait 12 months after treatment for syphilis or gonorrhea before you are eligible to donate blood. Most sexually transmitted diseases can be passed through blood. 

If you have genital herpes, venereal warts, or chlamydia, then you can be a blood donor. You may donate blood if you have chlamydia, venereal warts (human papillomavirus), or genital herpes and you are feeling healthy and well and meet all other eligibility requirements.

You must be at least 17 years old and in good health to be eligible to give blood. Guidelines on eligibility to give blood change from time to time, but the most up-to-date eligibility information can be obtained by contacting the American Red Cross blood center nearest you.