Are proteins, enzymes, or other substances transferred from a woman to a man during sexual intercourse, and what are the potential effects on his health?

From the Guidelines

During sexual intercourse, various biological substances including proteins, enzymes, hormones, and microorganisms can be transferred from a woman to a man, though the health effects are generally minimal for most healthy individuals. The primary transfer occurs through vaginal fluids, which contain proteins like immunoglobulins, cytokines, and various enzymes 1. These substances typically don't cause significant health impacts in men as they're either broken down in the digestive tract if swallowed or have limited absorption through genital tissues. Some components in vaginal fluids may have mild immunomodulatory effects, potentially influencing local immune responses temporarily. The vaginal microbiome can also be transferred, which might temporarily alter the penile microbiome but usually doesn't cause problems in healthy men.

Key Considerations

• The most significant health concerns relate to sexually transmitted infections rather than normal biological substances.
• Seminal fluid allergy is rare but possible, causing localized reactions in some individuals, as noted in the context of anaphylaxis to human seminal plasma proteins 1.
• The use of condoms can reduce the risk of acquiring sexually transmitted pathogens, including cytomegalovirus, herpes simplex virus, and human papillomavirus, as well as other infections 1. Overall, the transfer of normal biological substances during intercourse is a natural part of sexual activity and doesn't typically require medical intervention or concern for most healthy individuals. However, practicing safe sex, including the use of condoms, is crucial for preventing sexually transmitted infections.

From the Research

Substances Transferred During Sexual Intercourse

• Proteins and enzymes can be transferred from a woman to a man during sexual intercourse, as evidenced by the presence of various substances in female "sexual" fluids, including transvaginal transudate, female ejaculation (FE), and squirting (SQ) 2.
• FE is the secretion of a few milliliters of thick, milky fluid by the female prostate (Skene's glands) during orgasm, which contains prostate-specific antigen 2.
• SQ is defined as the orgasmic transurethral expulsion of tenths of milliliters of a form of urine containing various concentrations of urea, creatinine, and uric acid 2.

Potential Effects on Men's Health

• The transfer of microbes during sexual intercourse can have significant implications for men's health, including the potential transmission of sexually transmitted infections (STIs) 3, 4.
• The microbial transmission between seminal and vaginal fluids is a stochastic, passive diffusion similar to the random walk of particles, rather than driven by deterministic forces, with a transmission probability of approximately 0.05 4.
• The exchange of microbes during sexual intercourse can also have evolutionary implications, particularly from the perspective of sexual reproduction (selection), and may support the Red Queen hypothesis 4.

Enzymes and Proteinase Inhibitors

• Lysozyme, alpha-amylase, neutral proteinase, and plasminogen activator are most concentrated in the initial portion of the ejaculate that consists mostly of Cowper's gland and prostate gland fluids as well as spermatozoa 5.
• The concentration of high molecular weight proteinase inhibitors, such as alpha1-antitrypsin and alpha1X-antichymotrypsin, is essentially unaltered throughout the ejaculate fractions 5.