Niacin (Nicotinic Acid) vs Niacinamide (Nicotinamide): The Vitamin B3 Difference Explained

As different as chalk and cheese. That is perhaps the most apt description for nicotinic acid (niacin) and nicotinamide (niacinamide). While both are called Vitamin B3, they act very differently in the body.

One can make your skin turn beetroot red, while the other is a gentle ingredient in skincare products that helps repair cells.

This is a simple overview of what separates Niacin (nicotinic acid) from Niacinamide (nicotinamide): their chemistry, historical context, specific effects on the skin, and the reason for the skin-flushing effect of one but not the other.

Key Takeaways

• Niacin (nicotinic acid) and Niacinamide (nicotinamide) are both forms of vitamin B3, but they differ in chemical structure and biological behaviour.
• Niacin can cause a “niacin flush” by triggering chemicals that widen blood vessels and make the skin red; Niacinamide does not cause this reaction.
• Niacinamide is preferred in skincare because it helps strengthen the skin barrier and reduces inflammation without causing irritation.

Quick Glossary

• Pyridine ring: A six-sided molecular structure (the "skeleton" of both niacin and niacinamide).
• Carboxyl group (-COOH): An acidic chemical group found in niacin.
• Carboxamide group (-CONH₂): A neutral chemical group found in niacinamide.
• NAD⁺: A molecule that helps cells produce energy and repair DNA. Both niacin and niacinamide help the body make it.
• Prostaglandins: Chemicals that cause blood vessels to widen, leading to the niacin flush.
• Coenzymes: Small molecules that help enzymes do their job. NAD⁺ is a coenzyme involved in energy production and DNA repair.
• Melanosomes: Small containers filled with melanin (pigment) that determine skin colour.
• Melanocytes: Specialised cells that produce melanin and transfer it to other skin cells.
• Keratinocytes: The most common cells in the outer layer of skin – they receive melanin from melanocytes.

The Chemistry of Vitamin B3

To see why these compounds act differently, it helps to look at their structure.

Vitamin B3 refers to a group of related compounds, mainly nicotinic acid (niacin) and nicotinamide (niacinamide). Another form, nicotinamide riboside (NR), is being studied for its possible role in promoting longevity, but this article does not cover it.

All forms of B3 serve one main purpose: they are precursors to nicotinamide adenine dinucleotide (NAD⁺) and its phosphorylated partner, NADP⁺. These are coenzymes involved in over 400 reactions in the body. They cover energy metabolism, DNA repair, cell signalling, and antioxidant defence.

A Brief History of Vitamin B3

From Nicotine to Nicotinic Acid

The story begins, rather unexpectedly, with tobacco. In 1867, nicotinic acid was first synthesised through the oxidative degradation of nicotine using potassium chromate and sulphuric acid. The chemist Hugo Weidel described the compound more formally in 1873 during his studies of nicotine, though no one yet understood it had anything to do with nutrition.

Pellagra and the Vitamin Connection

It took decades to link nicotinic acid to human health. In 1937, biochemist Conrad Elvehjem at the University of Wisconsin isolated nicotinic acid from liver extract. He showed it could cure black tongue in dogs – a disease similar to pellagra in humans. Elvehjem and his team also found that nicotinamide was a cure factor. Both were designated as vitamin B3.

Why “Niacin”?

When vitamins began to be marketed directly to consumers in the 1940s, a problem arose. The name “nicotinic acid” was too close to “nicotine,” and the public understandably made unfortunate associations. The U.S. Food and Drug Administration allowed renaming: nicotinic acid became niacin (a contraction of nicotinic acid + vitamin), and nicotinamide became niacinamide.

What Is Niacin (Nicotinic Acid)?

Now look more closely at each molecule’s structure and role, starting with Niacin (nicotinic acid).

Niacin, also called nicotinic acid, is a molecule built on a six-sided ring structure (called pyridine) with an acidic group (carboxyl, -COOH) attached to it.

Nicotinic acid is found in foods such as meat, fish, legumes, and fortified cereals. Nicotinic acid has even been found in carbonaceous chondrite meteorites and in sample returns from the asteroids Ryugu and Bennu.

What Is Niacinamide (Nicotinamide)?

Niacinamide is the amide form of vitamin B3. It is almost the same as nicotinic acid, except it has a carboxamide group (-CONH₂) instead of a carboxyl group (-COOH).

Niacinamide works as a vitamin just like nicotinic acid, but its effects and side effects are different. It does not cause flushing and is the main form used in skincare products.

The Structural Difference: One Functional Group

The main difference between these two molecules is one functional group on the pyridine ring:

This substitution, swapping an oxygen for an amine, changes how the molecules bind to receptors. Niacin activates the GPR109A receptor, but niacinamide does not. This difference explains the flushing response and most of their other effects.

The Niacin Flush: Why Niacin Turns Skin Red

The most well-known difference between these two compounds is the flush caused by niacin, and its mechanism is well understood.

When nicotinic acid enters the body:

• It binds to a specific receptor called GPR109A (also known as HCA₂), which is found on immune cells and skin cells in the outer layer of the skin.
• This triggers a chain reaction that releases signalling chemicals (prostaglandins).
• These chemicals tell blood vessels under the skin to widen.
• More blood flows to the surface → skin turns red, feels warm, and may tingle or itch.

This usually starts 20–30 minutes after taking niacin and fades within 1–2 hours. Most people develop tolerance after a few weeks, and the flushing becomes less intense or stops altogether.

Niacinamide does not bind to the GPR109A receptor, so it does not trigger this cascade of events. No prostaglandins, no flushing. This is why niacinamide replaced niacin in most skincare products where the flush is undesirable.

Niacin and Niacinamide in Skincare

Niacinamide: The Topical Standard

Niacinamide is one of the most well-studied ingredients in cosmetic science. It is usually used in products at concentrations between 2% and 5%, but some products contain up to 10%.

Clinical trials have shown that niacinamide can:

• Sebum regulation: A 2% concentration has been shown to reduce sebum excretion rate, with visible improvement in oiliness and pore appearance within 2–4 weeks.
• Hyperpigmentation: At 5%, niacinamide helps fade dark spots by stopping melanosomes from moving from melanocytes to keratinocytes. It does not stop melanin production, but changes how it is distributed.
• Barrier function: Niacinamide increases the production of ceramides, fatty acids, and important barrier proteins in skin cells.
• Anti-ageing: At 4–5%, niacinamide can reduce fine lines and wrinkles, improve skin texture, and make skin more elastic. These benefits are linked to more collagen production and less activity of enzymes that break down skin structure.
• Anti-inflammatory: Niacinamide reduces the production of certain inflammatory chemicals in skin cells exposed to UV light. Using 5% niacinamide before sun exposure has been shown to reduce redness in clinical trials.

Niacinamide is easy to use in products because it is pH-neutral and dissolves in water. It is usually well tolerated by all skin types.

Nicotinic Acid: Rarely Used Topically

Nicotinic acid is rarely used in skincare products because it causes flushing. When applied to the skin, it activates the same receptor (GPR109A), leading to redness and irritation, which is not desirable in products meant to improve skin appearance.

Niacin vs Niacinamide: Side-by-Side Comparison

Here is a table that shows the main differences in properties and uses between niacin and niacinamide.

The Final Takeaway

Niacin and niacinamide are two forms of the same vitamin, but a small structural difference leads to big differences in how they work. Niacin is used as a medicine and can cause flushing, while niacinamide is gentle and widely used in skincare. Although they share a vitamin name and similar roles in the body, they should be seen as separate ingredients with different uses. For best results, it’s important to use the right form in the right way, not just the highest amount.