Human and animal studies show that a group of genes called the major histocompatibility complex (MHC) can influence odor. In general, females prefer the odor of mates with a dissimilar MHC — but this effect is reversed in women on oral contraceptive pills.
A study found that that single women preferred the odor of MHC-similar men, but women in relationships preferred the opposite. This means that that the use of contraceptive pills could influence mate preference.
According to FYI Living:
“The women on pills preferred men with similar MHC genes. Studies indicate that, ‘women consider the olfactory domain to be an important factor in their assessment of potential partners.’ Thus, due to serious alterations in odor preference, the use of oral pills could influence partner choice.”