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Dandruff and dry scalp – what’s the difference? Episode 33

What’s difference between dry scalp and dandruff? And how do you pick the best kind of dandruff shampoo for you? Also, in our Beauty Science News segment we ponder new research on antioxidants.

Show notes

Beauty Science News

I saw a pair of articles this week that caused me to rethink everything we’ve been told about antioxidants.

  • http://www.futurederm.com/2014/05/19/why-i-never-ever-use-a-self-tanner/
  • http://www.medicalnewstoday.com/articles/276589.php

Question of the week: What’s the difference between dry scalp and dandruff?

Prima asks…A stylist told me the cause of dandruff is sulfur in shampoos and conditioners. Is this true? If it is, why do people also say that weather has an effect on dry scalp?

Let’s just start by explaining the difference between the dandruff and dry scalp.

What is dandruff?

Dandruff is not just a flaky scalp. In fact, your scalp flakes ALL the time but you usually don’t see it because in a healthy scalp the flakes are microscopic. Dandruff occurs when the flakes are large and are accompanied by itching and inflammation.

There are 3 requirements for dandruff to occur:

  1. Oily scalp – Your scalp produces sebum on a regular basis
  2. Yeast – Your scalp must be colonized by a certain strain of yeast (Malassezia globosa). The yeast eat your scalp oil and “poop” out a potentially irritating compound called oleic acid.
  3. A sensitivity to oleic acid – this varies from person to person and explains why some people have no reaction while others develop severe dandruff.

When the scalp is irritated it becomes red and itchy and the body responds by increasing the rate of cell turn over. Now the cells flake off so fast that they clump together and form visible flakes.

Dry scalp is dry skin
Dry scalp, on the other hand, is just dry skin on your head. Your scalp can be dry just like the rest of your skin. It’s just usually less noticeable for a couple of reasons.

First it’s not exposed to frequent washing like your hands. Your scalp may be washed only once a day or every few days for some people. So the scalp has less exposure to drying surfactants.

Second the hair follicles on your scalp produce sebum which tends to keep the scalp moisturized. The skin on the rest of your body doesn’t have the same amount of oil. So there’s less exposure to drying conditions and more protection, but still, dryness can certainly cause your scalp to flake.

The Mayo Clinic has a nice summary of the factors that contribute to dandruff and dry scalp, let’s take a look at those and then we’ll talk about the cures.

Causes of scalp problems

Dry skin – the most common cause of flaking. As we discussed, these flakes are smaller and less oily and you’ll also find them on other parts of the body, such as your legs and arms.

Irritated, oily skin – can lead to seborrheic dermatitis, a condition marked by red, greasy skin covered with flaky white or yellow scales. Seborrheic dermatitis may affect your scalp and other areas rich in oil glands, such as your eyebrows, the sides of your nose and the backs of your ears, your breastbone, your groin area, and sometimes your armpits.

Infrequent shampooing – If you don’t regularly wash your hair, oils and skin cells from your scalp can build up, causing dandruff.

Other skin conditions – people with eczema (a chronic, inflammatory skin condition) and psoriasis (which is marked by a rapid buildup of rough, dry, thick scales) may look like they have dandruff but they don’t.

A yeast-like fungus (malassezia). Malassezia lives on the scalps of most adults, but for some, it irritates the scalp. This can irritate your scalp and cause more skin cells to grow. The extra skin cells die and fall off, making them appear white and flaky in your hair or on your clothes. Why malassezia irritates some scalps isn’t known.

Sensitivity to hair care products – can lead to contact dermatitis can cause a red, itchy, scaly scalp. (This is more likely if you dye your hair or shampoo too often.)

Cures for itchy, flaky scalp

If it’s just dry skin it will respond to moisturizing or to environmental changes. You can also reduce drying agents like shampooing too much.

On the other hand, if it’s dandruff you’re going to need a medicated shampoo. Dandruff treatments are over the counter drugs which means they have to use one of the approved active ingredients. These don’t all work the same way and some have more side effects than others so let’s take a look at these one by one.

Zinc Pyrithione

The most popular anti-dandruff active. Effective against dandruff and seborrheic dermatitis. Works well with almost no side effects. It even reduces irritation of surfactants.

It’s found in Selsun Salon, Head & Shoulders, and others.

Coal Tar

As the name suggests, this active ingredient comes from the coal manufacturing process. It treats dandruff, seborrheic dermatitis and psoriasis by reducing cell turnover. Coal tar is actually a keratoplastic which means it causes the skin to shed dead cells from its top layer and slow down the growth of skin cells. It tends to have a stronger residual odor which some people dislike.

It can be found in products like Denorex and Neutrogena T/Gel.

Salicylic acid

This beta hydroxy acid helps eliminate flakes. It works by causing the skin to swell, soften, and then slough or peel in areas where it is applied. Doesn’t really do much against the fungus. It may require a conditioner to prevent your scalp from becoming overly dry.

Two special warnings associated with Sal Acid shampoos: They should not be used on children or teenagers with the flu or chickenpox. And you should avoid getting salicylic acid shampoo on your genitals.

Can be found in products like “Ionil T Shampoo”.

Selenium sulfide

Another ingredient that both reduces cell turnover and fights malassezia. It’s used in “intensive versions” which indicates it’s even more effective, however, there are some issues:

May also have a little residual sulfur odor.
It may discolor blonde, gray or chemically colored hair.
It may damage jewelry so don’t shower with your bling on.

Found in Selsun Blue and the Intensive version of H&S.


Formerly available only by prescription, this antifungal drug fights the cause of dandruff. However it has several potential side effects: it may cause abnormal hair texture, loss of curl from a permanent wave, hair discoloration, and oiliness or dryness of the hair and scalp.

Found in Nizoral shampoo.

Piroctone olamine aka Octopirox

An active not currently approved in the US. Because of its solubility in water and alcohol it can be used to make clear products. (Most dandruff shampoos are creamy.) However it’s unstable in light so if you make a clear product and then show it off in a clear bottle the light will degrade the active ingredient and it won’t work. May also be inactivated by some perfume oils.

Not found in the U.S.

Prescription drugs

If none of these over the counter dandruff shampoos work for you, ask your doctor for prescription dandruff fighters like Loprox or steroid lotions.

Dandruff myths

We mentioned at the beginning that there’s a lot of misinformation around dandruff so let’s finish up today’s show by busting a few myths, starting with the ones Prima mentioned.

Sulfur in hair care products cause dandruff
Myth: Actually sulfur is part of anti-dandruff ingredients! It helps get rid of it, not cause it!

Weather causes dandruff
Myth: Low humidity can trigger dry skin which leads to flaking but weather alone does NOT cause dandruff.

You can catch dandruff from someone
Myth: Dandruff isn’t an infection, which means it can’t be caught from contact with people with dandruff. You have to have an individual sensitivity or predisposition to it.

Dandruff is caused by poor hygiene
Myth: While washing your hair helps, this is a common misconception. It’s actually our intrinsic susceptibility to irritation,  sebum (a substance found on our scalps) and a micro-organism that lives on our scalp that really causes dandruff. Of course, while dandruff isn’t simply a result of poor hygiene, washing your hair regularly with dandruff can certainly make a big difference.

Styling products cause dandruff
Myth: No, but some styling products leave a flakey residue that looks like dandruff. (From the resins that hold your hair in place.)

Dandruff is caused by dry scalp
Myth: This is a little redundant at this point but actually dandruff has nothing to do with dryness – rather it’s caused by too much oil.

If a shampoo says it removes flakes then it’s a dandruff shampoo
Myth: Some clever marketers imply their products are dandruff shampoos by talking about removing visible flakes (which ANY shampoo will do.) Burts Bees “Feeling Flakey” is an example.

Copper brushes cure dandruff
Myth: Copper does have anti fungal properties and although some people swear by this, we can’t find any evidence that it’s true.

The Beauty Brains bottom line

It’s important to understand whether you truly have dandruff or just dry scalp. Then you can decide how to best take care of your scalp. A ZPT-based shampoo is generally accepted as the best but there are several different active ingredients you can choose from if your scalp is particularly flakey. And now you know that sulfur in shampoos and the weather do NOT cause dandruff!

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Buy your copy of It’s OK to Have Lead in Your Lipstick to learn more about:

  • Clever lies that the beauty companies tell you.
  • The straight scoop of which beauty myths are true and which are just urban legends.
  • Which ingredients are really scary and which ones are just scaremongering by the media to incite an irrational fear of chemicals.
  • How to tell the difference between the products that are really green and the ones that are just trying to get more of your hard earned money by labeling them “natural” or “organic.

Click here for all the The Beauty Brains podcasts.

Comments on this entry are closed.

  • C AVINCENT June 3, 2014, 11:26 am


  • Sneza June 3, 2014, 12:20 pm

    I’m not sure why the self-tanner story makes you “re-think” antioxidants…. it takes the usual line (free radicals = bad), doesn’t it?

    I agree that the story about the McGill claims is an eye-opener / head-scratcher (get it? itchy head?).

    • Randy Schueller June 3, 2014, 1:37 pm

      I think Perry meant that the self-tanner article made him rethink the safety of self-tanners.

      • Sneza June 3, 2014, 4:16 pm

        Ah, yes — me, too.

  • Siobhan June 4, 2014, 2:24 am

    Great episode! You mention that if you just have dry skin on your scalp, as opposed to dandruff, this can be addressed by moisturising and other factors – could you elaborate? I’ve tried moisturising my scalp and it’s pretty damn hard!

    & by the by, I like the beauty fact or fiction segment. Some of the true headlines are more ridiculous than the falsehoods!

    • Randy Schueller June 4, 2014, 10:41 am

      We just meant that if your skin is dry it can be treated with moisturizers. But it’s certainly not easy to apply lotion to your scalp!

  • Laura June 5, 2014, 10:28 am

    I wonder if the hairdresser meant SULPHATES cause dandruff? I battled with “dandruff” for a good 20 years, until I started using a sulphate-free shampoo. Haven’t seen a single flake or been itchy since, close to two years now.

  • Chris June 5, 2014, 3:14 pm

    Great show guys and I too love the beauty fact or bulls*** segment. Listening to Perry fail always cheers me up. Don’t worry you’ll get it next time! 😀

  • Rachel July 7, 2014, 9:59 am

    I have a question. I have a dry scalp, but greasy hair what should I do? I used this shampoo that is for dry hair and my scalp problems went away, but my hair always looked disgusting and felt icky, then I tried to use a clarifying shampoo for oily hair and my problems came back somewhat, I went back to the dry hair shampoo and again my hair was nasty, from then on I’ve been using shampoo for all hair types or normal hair and my hair is usually decent but my scalp is awful again. What should I do? Or is it that my scalp is irritated by harsher, but more effective cleansers?

    • Randy Schueller July 7, 2014, 7:26 pm

      You might try using a dry scalp shampoo and balancing it with a good conditioner.

  • Allie August 1, 2014, 6:07 pm

    Will repeated exposure to the salicylic acid in some dandruff shampoos result in any weakening of/damage to the hair? Or does the pH of T/Sal fall within an erosion-free zone?

    • Randy Schueller August 2, 2014, 7:32 am

      Allie: I’ve never seen any data indicating that the pH of sal acid dandruff causes any damage to hair. I really don’t think it’s a problem but if your’e concerned you might try switching between different types of active agents like ZPT.