Why generic hair advice fails, and what conditional advice looks like

Advice about hair almost always starts life as a conditional sentence. If your scalp is oily, wash more often. If your hair is coarse and curly, do not. Then it gets shortened for a headline, a caption, or a thirty-second video, and the part that made it correct is the part that gets cut, because conditions are long and instructions are short.

What reaches you is a bare instruction with the confident tone still attached. It sounds like a rule about hair. It is a rule about one kind of hair, and you have no way of knowing which kind, because that information was removed before you saw it.

The result is a reader who tries three pieces of advice, gets two bad outcomes, and concludes that their hair is difficult. Their hair is ordinary. The advice was sorted for someone else.

Take the most common scalp complaint there is. The American Academy of Dermatology's dandruff page names the active ingredients to look for, which are zinc pyrithione, salicylic acid, sulfur, selenium sulfide, ketoconazole and coal tar. So far so general. Then it splits.

For fine or naturally straight hair, or an oily scalp, the page says to wash often, and gives the example of shampooing daily and using the dandruff shampoo twice a week. For coarse or naturally curly or coily hair, it says to wash when needed and use the dandruff shampoo about once a week, if tolerated, and to apply it only to the scalp, because the ingredients that treat dandruff can dry the hair.

One page, one condition, two schedules that differ by a factor of two, plus a placement rule that applies to one group and not the other. Now picture that same guidance as a caption: 'use dandruff shampoo twice a week'. Half the readers who follow it will dry out hair that was already dry. The dandruff and flaky scalp guide has the full treatment side.

The same organisation's healthy hair page puts straight hair with an oily scalp at possibly shampooing every day, and dry, textured, curly or thick hair at shampooing when needed, with a floor of at least once every 2 to 3 weeks. Its curly hair page repeats that floor and adds that washing curly hair too often leaves it dry, frizzy and hard to manage. Its guidance for Black hair gives a schedule of once a week or every other week.

Read those together and the honest range for a human being runs from daily to fortnightly. That is not a small spread around a average. There is no average in the middle worth quoting. The question 'how often should I wash my hair' has no answer until someone has looked at your scalp and your texture.

So when an article gives you a single number, the number is a guess about who is reading. Our position: a wash frequency you were given without being asked what your scalp does is worth ignoring. The mechanics and the schedule live at how often to wash your hair.

This is the clearest example on the page, because the two instructions are one sentence apart in the source. The American Academy of Dermatology says that if you have fine or straight hair, apply conditioner to the ends. If your hair is dry or curly, apply it to the entire length. Its curly hair page goes further and says to condition all your hair rather than the ends alone, and to add an oil or leave-in afterwards.

Same product, same step, opposite placement. A person with fine hair who conditions root to tip gets hair that falls flat by the afternoon and reads as greasy. A person with coily hair who conditions only the last few centimetres stays dry, tangles, and then blames the product.

Neither of them did anything careless. They both followed conditioner advice they read somewhere. The instruction they needed was three words longer.

Here the advice does not shift by degree. It inverts. The American Academy of Dermatology's styling page says most people should handle wet hair as little as possible, because wet hair breaks more easily when combed or brushed. In the next sentence it says that people with tightly curled or textured hair should brush their hair when wet, to reduce the chance of breakage.

Its healthy hair page lines up with that: detangle wet hair with a wide-tooth comb rather than a brush, and if your hair is thick and curly, the best moment to comb is in the shower before the conditioner is rinsed out, while straight hair should be left to dry partly first.

If you have ever read two hair accounts and thought one of them must be lying about wet brushing, this is why. Both were right. Neither said for whom.

Heat advice is where generic rules do the most expensive damage, because the damage does not show for weeks. The general instruction is real: the American Academy of Dermatology says flat irons should be used on dry hair at a low or medium setting, no more often than every other day, and that excessive heat can damage any hair type.

Then the condition arrives. Its guidance for Black hair says to press with a ceramic comb or iron no more than once a week, using a device with a dial, at the lowest possible temperature that gives the style you want, and adds that a higher temperature may be necessary for thicker, coarser hair. So the ceiling moves with strand thickness, and the frequency moves with hair type, and both of those are readings about you.

A number copied from a video is a number chosen for the person holding the camera. If you want the temperature side in depth, it is at heat damage and heat protection.

There is a fair reason for this. Conditional advice is harder to write, longer to read, and does worse in every format that rewards being shared. 'Stop washing your hair every day' fits in a caption. 'Stop washing your hair every day if your scalp is not oily and your hair is coarse or curly, and keep washing daily if it is fine and your roots shine by evening' does not.

Product marketing pushes the same way. A bottle sells to more people if the instruction on it applies to everyone, so the label says 'for all hair types', which is a marketing claim rather than a reading.

Some of it is also an honest limit rather than a shortcut. Dermatologists write for a public that does not know its own hair type. The American Academy of Dermatology's curly hair page ends by saying that trial and error are often needed to find the best routine, which is a straight admission that even good conditional advice leaves work for the reader.

Advice you can act on has three parts: the instruction, the condition it depends on, and the thing you will see if it was right for you.

Compare. Generic: 'use less conditioner'. Conditional: 'your hair is fine and it is going flat by mid-afternoon, so keep conditioner below the ears this week, and check on day two whether the roots still lift.' The second one names the reading, gives a placement, and gives you a test. If the roots still fall flat, the reading was wrong and you change it, which is a thing you cannot do with the first version.

The third part is the one most advice skips, and it is the part that protects you from bad advice. An instruction with a visible check attached can be proved wrong in a week. An instruction without one can be followed for a year while nothing improves. This is why hair condition, rather than the cut, is what decides how your hair looks on an ordinary day, and why reading your hair before the cut tends to change more than a new shape does.

Put two real readings side by side. Person A has fine, straight hair, high density, an oily scalp, roots that shine eight hours after washing, no colour, no heat tools. Person B has coarse, tightly coiled hair, medium density, a scalp that flakes when the gap between washes gets long, colour on the mid-lengths, a flat iron on Sundays.

Now give them both the same popular instruction: wash twice a week, condition from root to tip, brush before showering, air dry. For Person A that is four wrong moves out of four. The gap is too long for their scalp, the conditioner flattens hair that was already fine, and brushing dry straight hair before a shower adds friction to hair that does not need it. For Person B the same four are close to correct, and the one to check is whether twice a week is more washing than their hair tolerates.

Nothing about that instruction is dishonest. It was written by somebody whose hair is like Person B's, for readers they assumed were the same. The failure is structural, not moral, and it repeats every day across the whole subject.

Four words. Put them to every hair rule you meet, including the ones on this site. If the article, the video, the label or the assistant cannot answer, you have learned what you needed, which is that the advice was not sorted for you.

The question also works on yourself. Before you follow something, say out loud which reading it depends on, and whether you match it. If you cannot name your own curl pattern, strand thickness, density and scalp state, that is the gap to close first, and the hair type chart takes two minutes.

This is the whole reason the Kurli AI Specialist reads photographs before it writes anything. The plan it returns attaches a reason to every step, so each instruction carries the reading it came from and you can argue with it. Advice you can argue with is the only kind worth following.