The ABC/C11 gene determines both the type of earwax a person has and their armpit odor. A change in a single base in the code for this gene can cause the gene not to function.
People with a functioning ABC/C11 gene have wet earwax and body odor, while those with the gene variant causing loss of function have dry earwax and little or no body odor. Loss of function of the ABC/C11 gene is very common among East Asian populations (80-90% of the population!), but fairly rare in other populations (1 – 3% of Caucasians).
So what exactly does this gene do? The ABC/C11 gene (A/TP-binding cassette transporter sub-family C member 11) codes for a protein that is involved in transporting molecules across cellular membranes. It is involved in the transport of lipophilic compounds, bile acids, conjugated steroids, and the substance that is in apocrine sweat and in earwax, thus causing body odor and wet earwax.
Variants of this gene are also involved in resistance to antiviral and anticancer drugs.[ref] The wet earwax allele was also associated with a higher risk of breast cancer in Japanese women, but not in women of European descent.[ref] [ref]
There was an interesting article in Scientific American a few years ago looking into the fact that those who genetically don’t have smelly pits often unnecessarily still wear deodorant. Other research showed that those with the ‘no body odor’ variant sometimes had other sources of body odor or social reasons for wearing deodorant.[ref]