Continuously updated · 7 variants · last reviewed Sep 5, 2026
Nearly everything else on this site is a probability. A variant nudges the odds of a condition, or the dose of a drug, and you could never tell from the inside which way your own copy fell. Smell and taste are the exception: the variant does not shift a risk, it changes the perception itself. One person smells the asparagus. The person next to them does not. Both are right about what they experienced.
This is also where the rest of the site connects. What tastes bitter decides what gets eaten, what gets eaten shapes the diet, and diet sits upstream of a good number of the conditions we cover. Losing smell can be an early sign in neurological disease. Flavour is not a curiosity bolted onto a genetics reference — it is where the genome meets food.
A smell that is obvious to one person and simply absent for another
A "specific anosmia" is blindness to one particular smell, with the rest of someone's sense of smell working normally — the cleanest demonstration that olfactory receptor genes are personal in a way most genetics is not. Two independent, well-replicated examples: whether the sulfurous compound asparagus metabolism produces in urine registers as a smell at all, and whether the compound behind a "fishy" or "fresh fish" smell is detected the same way for everyone.
OR2M7 · rs4481887
Read the genotypes → StandardTAAR5 · rs41286168
Read the genotypes →Written up in full: Smell Perception and Specific Anosmias
Why sudden smell loss became one of the most reported COVID symptoms
Sudden loss of smell or taste was one of the earliest, most widely reported COVID-19 symptoms, and it turns out to have a real genetic component: a locus near UGT2A1/UGT2A2, genes expressed in the tissue lining the nose, found in a study of over 33,000 people who had COVID-19. It is a modest genetic contributor to a viral, not an inherited, event — worth knowing about, not a diagnosis on its own.
Written up in full: Smell Perception and Specific Anosmias
Not what you smell — what you produce
A genuine outlier on this page: not a variant that changes what someone perceives, but one that changes what their own body produces. A single coding change in ABCC11 decides whether earwax is wet or dry, and the same change tracks with how much odor-causing secretion apocrine sweat glands produce — one of the cleanest single-SNP-to-visible-trait links in human genetics, and the reason its population frequency differs so sharply by ancestry.
Written up in full: Smell Perception and Specific Anosmias
Why the same food is not the same food
Taste receptors sit on the tongue and read molecules directly, so a change in the receptor is a change in the flavour. The bitter receptor TAS2R38 is the classic case: three coding changes travel together, and which pair you inherit decides whether a whole family of vegetables tastes bitter or tastes of almost nothing.
TAS2R38 · rs713598
Read the genotypes → StandardTAS2R38 · rs1726866
Read the genotypes → StandardTAS2R38 · rs10246939
Read the genotypes →Written up in full: Bitter Taste Perception (TAS2R38)
Vanillin
C8H8O3
The aromatic ring your olfactory receptors read as vanilla.
Phenylthiocarbamide (PTC)
C7H8N2S
The bitter molecule TAS2R38 binds — the compound the classic taster test is run with.
Both are aromatic — a ring with a particular set of groups hung off it. A receptor reads that shape, and a coding change in the receptor changes what the shape is read as. That is the whole mechanism, and it is why a single base can decide what a food tastes like.
Solid lines are connections this site curates. Dashed lines mean the two ends share a research paper — worth knowing, and not a claim that one explains the other.
Read from the other end — every paper that mentions these positions beside another subject — on the smell and taste topic page.
The one part of this site where a variant does not shift a risk — it changes what someone actually perceives, like whether asparagus smells the way it does to someone else.
Yes — uniquely on this site. Chemosensory variants change perception itself, so a reader can check a result against what they actually taste or smell, unlike a risk variant that can't be felt from the inside.
Because it connects to everything else here: what tastes bitter shapes what gets eaten, diet sits upstream of many conditions this site covers, and losing smell can be an early sign in neurological disease.
This page is the curated index — the specific chemosensory groups with their genotypes and sources. The topic page instead counts co-mentions: every paper that mentions one of these positions alongside another subject.