Ammonia has been in hair color for over a century. It works, but it is harsh. More brands now leave it out, and the words "ammonia-free" turn up on a lot of boxes. It helps to know what that actually means before you buy.
What ammonia does in hair color
Color has to get inside the hair to last. The outer layer, called the cuticle, lies flat and closed. Ammonia raises the pH and forces it open. Pigment can then reach the cortex underneath, where it stays.
The trouble is what else happens on the way. A high pH swells the hair and pulls moisture out. Once the cuticle has been forced open like that, it rarely closes fully again. That is why colored hair can end up feeling dry and rough.
Ammonia also has a sharp smell that most people know from the salon. It can sting the scalp and make your eyes water.
Why brands are dropping it
Two things changed. Customers started reading ingredient lists, and the alternatives got better.
Most ammonia-free formulas use ethanolamine instead. It does the same job at a lower pH. The color still lasts, but the hair takes less of a beating, and the smell is much milder.
Ethanolamine is not magic. It is still a chemical, and it still opens the cuticle. It simply does it more gently.
Ammonia-free is not the same as natural
This is where labels get confusing. The two phrases often sit side by side, but they mean different things.
Ammonia-free tells you one ingredient is missing. It says nothing about the rest of the formula. A dye can be free of ammonia and still contain SLS or parabens, which are the two most worth avoiding.
Natural is vaguer still. There is no legal definition of the word in cosmetics. A brand can print it on the box with very little to back it up.
Then there is henna, which really is plant based. It works in a different way. Henna coats the hair rather than changing it from inside. It is difficult to remove and can react badly with other color. On gray hair it often turns brassy or green.
So if you want lasting color that covers gray, a plant dye is usually not the answer. What you want is a permanent color with a shorter, cleaner ingredient list. That is the middle ground most people are actually looking for.
What the ingredients actually do
Turn the box over and the list can look intimidating. Most of it has a purpose. Here is what the main names mean, and which ones are genuinely worth avoiding.
Ammonia
Ammonia is the alkaliser in most traditional hair colors. Its job is to raise the pH so the cuticle opens and pigment can get in. It does that quickly and reliably, which is why it stayed in use for so long.
The cost is the pH itself. At that level the hair swells, loses moisture and struggles to close properly afterwards. The smell is the other part most people notice.
Ethanolamine does the same job at a lower pH. The color still develops properly, but the hair goes through less on the way. That swap is what most gentler formulas have made.
PPD
PPD, or p-phenylenediamine, is what makes permanent color permanent. It is a small molecule that slips into the hair and then develops into a larger one. Once that happens the color cannot easily wash back out.
It matters most in darker shades. Without PPD or something like it, deep browns and blacks would fade within a few weeks. Almost every permanent color on the market relies on it.
PPD is also the most common cause of allergic reactions to hair dye. That is worth knowing rather than worrying about. Reactions are not common, but they do happen, and sensitivity can build up slowly over years of coloring.
It is a regulated ingredient. Maximum levels in hair dye are set in law and reviewed by scientific committees before products reach the shelf. The sensible precaution is simple. Do a patch test 48 hours before you color, every time, even with a product you have used for years. We go through the whole subject in our guide to PPD in hair dye.
Resorcinol
Resorcinol works alongside PPD. It is what the industry calls a coupler. It reacts with the developing dye to produce specific tones rather than adding color of its own.
Cool and ash shades lean on couplers the most. Without them those tones drift warm, and the result looks nothing like the picture on the box.
Like PPD it is used at levels set by cosmetics regulation, and it has been assessed repeatedly by the EU scientific committees. It has a job to do, and at controlled levels it does it well.
Some people still prefer to keep their overall exposure low. If that is you, look at the whole picture rather than one line on a label. How often you color your hair matters more than any single ingredient.
SLS
SLS, or sodium lauryl sulfate, is a strong detergent. It shows up in a lot of shampoos because it foams well and strips oil efficiently. Neither of those is helpful around fresh color.
It irritates the scalp for many people. It also pulls pigment out of colored hair faster than a gentler cleanser would, so your color fades sooner than it should.
This one is worth avoiding completely. Check your shampoo and conditioner as well as your color, because that is usually where it hides.
Parabens
Parabens are preservatives. They stop bacteria and mold growing in a product, which is a real job that something has to do.
The concern is that they can be absorbed through the skin, and that some of them weakly mimic estrogen. The research is not settled, and regulators still allow them at limited levels.
Even so, good alternatives exist, and there is little reason to accept them. This is the other one to avoid completely.
Does ammonia-free color cover gray hair?
Yes, as long as it is permanent. This is the question we get asked most.
Gray hair has lost its pigment. It is also coarser and less porous, so it takes color more slowly than the rest of your hair. A semi-permanent dye will simply wash out and leave the gray showing again.
A permanent ammonia-free color works differently. It places pigment inside the hair and stays there. The lower pH means it takes its time, so leave it on for the full development time on the instructions.
If more than half your hair is gray, pick a shade close to your natural color. The result looks far more even that way. You can see our full range of shades here.
Getting the best result at home
A few habits make more difference than the product you pick.
Start with unwashed hair. The natural oils give your scalp a bit of protection.
Stay within two shades of your own color. Bigger jumps rarely look natural when you do them at home.
Section your hair and start at the roots. Roots develop faster because of the warmth from your scalp.
Use the full development time. Rinsing early is the most common reason color fades within weeks.
Wash with a color safe shampoo afterwards. Sulfates strip pigment quickly, and all that careful work goes down the drain.
