What Makes Peppers Hot? Capsaicin and the Five Capsaicinoids

Q: What is the difference between capsaicin and dihydrocapsaicin?

They are near identical in structure and both extremely pungent. Together they account for roughly 80 to 90 percent of a pepper's total heat. Dihydrocapsaicin is detectable at a slightly lower concentration, so it is marginally more potent by threshold.

The short answer: Capsaicin is the main compound that makes chili peppers hot. But a pepper's burn is really built by a family of related compounds called capsaicinoids, and the exact blend is what gives each variety its signature heat. Two peppers can share the same Scoville rating and still feel completely different.

Scoville Heat Units measure how much total capsaicinoid a pepper carries. They say nothing about how it burns: fast or slow, front of the mouth or deep in the throat, a quick flash or a long ache. That comes from the mix of compounds below. There are more than twenty capsaicinoids, but five do nearly all the work.

How the burn happens: Capsaicinoids bind a nerve receptor called TRPV1, the same sensor that normally fires around 43 C (109 F) to warn you of real heat. The molecule fools it, so your brain reads "burning" with no actual temperature involved. Each capsaicinoid grips and releases TRPV1 at its own pace, which is why each one lands in a different place and lasts a different length of time. (Source: PMC6639979; Chile Pepper Institute.)

The five capsaicinoids

Capsaicin

~50 to 69% of the mix

What it is: The principal capsaicinoid and the molecule the Scoville scale is built on. It is the benchmark every other compound is measured against.
Its role: The dominant driver of heat in virtually every variety.
Burn: The "typical" chili burn: mid mouth and palate, into the throat and back of the tongue. Moderate onset, strong persistence.

Dihydrocapsaicin

~22 to 36% of the mix

What it is: Capsaicin's near twin. Together, the two make up roughly 80 to 90% of a pepper's total pungency.
Its role: Co-dominant heat. The body of the burn alongside capsaicin.
Burn: Very similar to capsaicin: throat forward and persistent. By detection threshold it is actually a hair more potent (0.049 vs 0.080 ppm). Slow to fade.

Nordihydrocapsaicin

~7% of the mix

What it is: The gentlest of the five, described in sensory studies as the "least irritating."
Its role: The source of the immediate, forward heat: the flash you feel before you have even swallowed.
Burn: Front of the mouth and palate, a "mellow warming effect" that arrives instantly and fades quickly. Bright and fruity rather than punishing.

Homodihydrocapsaicin

~1 to 2% of the mix

What it is: A trace component with an outsized effect: tiny in quantity, enormous in memory.
Its role: The lingering punisher, disproportionately responsible for the deep, long burn of superhots.
Burn: Harsh and sharp, with a delayed onset that builds in the throat, back of the tongue, and chest, then stays for a long time. This is why a Reaper keeps going long after you have swallowed.

Homocapsaicin

~1 to 2% of the mix

What it is: The least studied of the five, present in small amounts in most varieties.
Its role: A minor contributor that rounds out the slow, long-chain end of the profile.
Burn: Grouped with the lower-pungency, longer-lasting capsaicinoids: a supporting note rather than a lead.

How the mix shapes the burn

Picture a pepper's heat as a wave with a front, a body, and a tail:

The frontNordihydrocapsaicin: instant, forward, fades fast.

The bodyCapsaicin plus dihydrocapsaicin: the main mid mouth and throat burn that carries the intensity.

The tailHomodihydrocapsaicin: the slow, deep, long-lasting ache.

Shift the ratios and you reshape the whole experience. A variety heavy in nordihydrocapsaicin reads as bright and quick. One with elevated homodihydrocapsaicin feels brutal and never-ending, even at the same SHU. The Chile Pepper Institute formalizes this as a five-part heat profile: Development (how fast it builds), Duration, Location, Feeling (a sharp prickle versus a flat coated heat), and Intensity (the SHU number, the only part Scoville captures).

The cousins with no bite: capsinoids

Capsinoids (capsiate, dihydrocapsiate, and nordihydrocapsiate) share the same backbone as capsaicinoids but swap one chemical bond, an ester for the capsaicinoids' amide. That tiny change makes them roughly a thousandth as pungent and unstable on contact, so they deliver the flavor and metabolic effects with almost no burn: "heatless heat." They are concentrated in non-pungent cultivars. If a sweet pepper still tastes faintly warm, capsinoids are why.

Frequently asked questions

What makes peppers hot?

Capsaicin, a compound made in the white pithy placenta inside the pepper. It binds the TRPV1 heat receptor in your nerves and triggers a burning sensation even though no real heat is present. Related compounds called capsaicinoids add to and shape that burn.

What are capsaicinoids?

The family of pungent compounds in peppers. Capsaicin is the most abundant, followed by dihydrocapsaicin, nordihydrocapsaicin, homodihydrocapsaicin, and homocapsaicin. Their blend determines a pepper's heat profile.

What is the difference between capsaicin and dihydrocapsaicin?

They are near-identical in structure and both extremely pungent. Together they account for roughly 80 to 90% of a pepper's total heat. Dihydrocapsaicin is detectable at a slightly lower concentration, so it is marginally more potent by threshold.

Which capsaicinoid causes the long lingering burn?

Homodihydrocapsaicin. It is present in tiny amounts but has a delayed onset and a very long duration deep in the throat and chest, which is why superhots keep burning well after you swallow.

Do all peppers contain capsaicin?

No. Sweet peppers like bells carry little to none because a single gene (Pun1) is switched off. Some sweet types instead contain capsinoids, the non-pungent cousins.

Want to feel the difference yourself?

Grow a few side by side. Start with a classic Carolina Reaper, a Peach Ghost, and a 7 Pot Primo, or browse our hottest varieties and the full seed catalog. New to superhots? Read our guide to germinating super hot pepper seeds first.

Sources: Kosuge and Furuta (1970), "Studies on the Pungent Principle of Capsicum," Agric. Biol. Chem. (capsaicinoid abundances). Krajewska and Powers (1988) and Bosland et al., "Sensory properties of chile pepper heat," Food Quality and Preference (sensory burn profiles and the Chile Pepper Institute heat-profile attributes). Schneider et al. (2014), detection thresholds for capsaicin versus dihydrocapsaicin. PMC6639979 (TRPV1 mechanism). Abundance and pungency figures vary by variety and method; values shown are representative ranges.