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Itchy, dry, red scalp. It’s embarrassing, painful and frustrating. And that’s just the way it looks. Having a scalp which is suffering these symptoms is also incredibly itchy, painful and can even sting and burn.
Is any shampoo safe?
Will any scalp treatment work?
Fact: the signs of contact allergy or irritant reaction to shampooing products can look and present exactly like dandruff and psoriasis. You read that right, a badly chosen dandruff shampoo can actually exasperate your condition.
It’s easy to waft this away.
I’ve been using the same shampoo for months/years with no issue – it definitely cannot be my shampoo.
I used this shampoo a few days ago – it didn’t cause me a reaction straight away so it definitely cannot be my shampoo.
Fact: allergic contact dermatitis is not immediate. It can also take months and years of exposure to build.
This is why shampoo allergy can be enormously hard to pinpoint.
If you’re beginning to see that your scalp symptoms could be more than just dandruff or seborrheic dermatitis – keep reading. We spoke to Matthew Zirwas, MD, board-certified dermatologist at Bexley Dermatology, and 15 year expert in working with common, but difficult to treat, dermatologic diseases and problems. And we spoke to Ruth Holroyd, founder of the award-winning blog What Allergy to find out more.
During the course of this article you’re going to learn;
- What is an allergy and how do shampoo allergies develop?
- What is the difference between an allergy and an irritation? – helpful if you’ve previously had a patch test
- What shampoo ingredients cause allergies?
- What is usually the first sign of contact dermatitis?
What is contact dermatitis?
Contact dermatitis is an allergy which is developed because of continual exposure to a potentially allergenic ingredient. Your skin, scalp and immune system have what is called a sensitization threshold. Meaning your body can handle allergenic ingredients at a pre-determined amount. This is not the same for everyone.
Allergens are ingredients like fabric dye and fragrances which;
- Have a small molecular size allowing them to penetrate the skin quickly and effectively
- Are able to bond with skin proteins – this creates a much bigger molecule that can be presented to and recognized by your body’s immune system
- Are recognized by your body as foreign
Scientists can use what a molecule looks like to understand if it has the potential to cause allergic contact dermatitis. This is called the structure-activity relationship (SAR). New and existing ingredients can then become a predicated sensitizer, possible sensitizer, predicted non-sensitiser or not predictable due to confusing/insufficient data.
Note; Recently published studies have demonstrated that in vitro assays i.e. an experiment which is not conducted on live animals but instead in a test tube has shown a strong correlation with original testing which was completed on animals. However that SAR approaches did not. The future of allergen prediction is in vitro.
- Vesicles – can look like blisters/papules/hives
- Contact eczema
The important question is – how do you tell if you’re allergic to your shampoo or if it’s a less life-changing irritancy reaction?
What’s the difference between irritant vs allergic contact dermatitis
When an ingredient irritates your skin you can easily mistake irritant contact dermatitis for allergic contact dermatitis.
The major difference between both conditions is the area of effect.
Irritant contact dermatitis – the most common kind – usually impacts only the area it’s applied to. For example, your skin may tingle or sting after the use of a shampoo, but only exactly where the shampoo has been used.
Allergic contact dermatitis, on the other hand, can cause the body to react over a greater area than that which was exposed to the allergen. As Dr. Zirwas explains, “the most common areas affected off of the scalp when people have allergy are the eyelids, in front of the ears, the jawline, and the neck.”
“The most common thing I diagnose in my eczema center is eyelid, neck or facial dermatitis being caused by allergy to an ingredient in shampoo. In many of these patients, they don’t even get a rash on their scalp. In dandruff/seb derm patients they usually assume it is their dandruff or seb derm spreading.”
Irritant contact dermatitis is not a primary reaction of your immune function to a foreign invader. Irritants instead break down your skin’s natural barrier which therefore now becomes ‘leaky’. When skin is leaky it becomes dehydrated, easily irritated and reddened. Due to the leaky nature of skin suffering from irritant contact dermatitis – stinging and burning sensations are common. Leaky skin also reacts indiscriminately – you may find whatever you put on your skin – it tingles, stings or burns.
In contrast to allergic contact dermatitis, having irritant contact dermatitis does not mean you need to avoid all potentially irritating ingredients forever more. It does not mean that when you are exposed to even a small amount – your skin will react in the extreme. This is the definition of sensitization, not irritant contact dermatitis.
In the case of irritant contact dermatitis, once the skin is healed and your skin barrier is restored, you may go on to use products with potentially irritating ingredients without reaction.
In the case of allergic contact dermatitis once the skin is healed you are extremely likely to always and forever more be allergic. This means exposing yourself to the smallest amounts of the ingredient you have developed an allergy to will always cause your skin to react. This typically happens within hours of exposure.
In appearance, allergic contact dermatitis can often cause swellings and raised areas of skin which ultimately cause blistering. Overuse of irritating personal care products – like shampoo – rarely results in blistering. Irritation is also usually fairly quick, whereas allergic contact dermatitis – after allergy has developed occurs hours post exposure. Allergic contact dermatitis symptoms are also likely to be much more severe.
How do you know if your scalp has a shampoo allergy?
There is 1 primary way in which a doctor or dermatologist can officially diagnose you with a contact allergy to ingredients found in shampoo. This is by patch testing. Small amounts of known allergens are placed onto 1cm patches which are then placed onto your skin.
Note; Dermatologists advise allergic reactions can take up to 2 weeks to develop with patch testing.
You can understand what to expect during a patch test by reading this 4-page leaflet from the British Association of Dermatologists.
Note; studies show of patients with eczema who are suspected of having a contact allergy to fragrance only 10.3% show positive results. This can be explained, in part, to be because the fragrances used in patch testing does not include all contact allergens – only those which most commonly cause a reaction. Therefore a negative patch test does not mean you do not have an allergy. However, a negative patch test could also mean you are suffering from irritant contact dermatitis.
What shampoo ingredients can cause allergy?
The Scientific Committee on Consumer Safety has identified 85 fragrance ingredients which are established contact allergens in humans. The problem is, manufacturers are not legally obliged to disclose the ingredients in their fragrances. Here’s why – the FDA requires the list of ingredients under the Fair Packaging and Labeling Act (FPLA). This law is not allowed to be used to force a company to tell “trade secrets.”
This is a real problem. As Ruth Holroyd explains, “the growth in allergies has seen a big rise in free from foods but what about the skincare products you use? It is just as important to understand what you use on your skin when you have allergies, eczema, dermatitis or psoriasis.”.
Things are a little brighter over in Europe. At the time of writing, the EU has mandated that 26 identified allergens must be declared on an ingredients label. Many of these are ingredients naturally found in fragrance or essential oils. Most essential oils and fragrance mixes contain only small quantities of allergens – therefore these will be listed on the bottom of the ingredients list.
The 26 EU declarable allergens are known as;
- Amyl cinnamal
- Benzyl alcohol
- Cinnamyl alcohol
- Amylcin-namyl alcohol
- Benzyl salicylate
- Anisyl alcohol
- Benzyl cinnamate
- 2-(4-tert-Butylbenzyl) propionald-hyd
- Benzyl benzoate
- Hexyl cinnam-aldehyde
- Methyl heptin carbonate
- Oak moss and treemoss extract
- Treemoss extract
Take for example allergen #19 – benzyl benzoate – this ingredient is a natural component of Peru Balsam and essential oils of Jasmin and ylang-ylang. In the EU, you do not have to remember that these ingredients also contain benzyl benzoate – because by law they must be separately written on the ingredients list.
Unfortunately, there’s still an additional 59 allergens declared by Scientific Committee on Consumer Safety that aren’t currently labeled either side of the Atlantic. The easiest way to protect your sensitive scalp from allergic contact dermatitis is by choosing a fragrance and essential oil free shampoo.
Note; Some preservatives and a handful of other ingredients used in shampoo products are more recently suspected allergens, these include;
- Formaldehyde releasers e.g. DMDM Hydantoin, Imidazolidinyl Urea, Diazolidinyl Urea
- Cocamidopropyl Betaine
- Cetrimonium Chloride
- Iodopropynyl Butylcarbamate
- Tetrasodium EDTA
- Butylated Hydroxytoluene
- Some (but not all) alcohols
But this is still only scratching the surface. The Contact Dermatitis Institute has put together a fantastic searchable database of ingredients known to cause allergic contact dermatitis. If any of them are present in a shampoo, we’ll warn you.
What shampoo ingredients can cause irritation?
The most common type of shampoo ingredient known to cause irritation is the ingredient making up the base and activity of all shampoos – cleansing agents aka surfactants. These ingredients can denature skin proteins and therefore break down your skin barrier.
Whether surfactants are or are not irritating to your skin doesn’t only depend on whether the formula contains them – but also the amount it uses and the overall pH and formula of the product.
These are however the most irritating surfactants as per published study data;
- Sodium Lauryl Sulfate
- Sodium Laureth Sulfate
- Cocamidopropyl Betaine
- Ammonium Lauryl Sulfate
- Sodium Myreth Sulfate
- Sodium Lauroamphoacetate
These ingredients are often some of the first on the ingredients list on a bottle of shampoo. The most commonly found are at the top of this list.
Remember how irritant contact dermatitis is different from allergic contact dermatitis?
Once your skin barrier is healed you may be able to use these ingredients in small quantities with no reaction.
What should you do now?
If you suspect you have allergic contact dermatitis check your scalp care products for all of the ingredients listed in this article including the word perfume or fragrance – if you see any of these – switch your shampoo today.
If you’ve had a patch test resulting in negative allergy results – we still advise you to do this – a combination of an irritant plus allergen can increase its penetration and potential biological effect.
Keep reading our reviews too. We warn of over 100 ingredients that have caused irritant or allergic reactions in people.
And luckily for you, we have developed a unique tool whereby you can search for any shampoo we’ve reviewed, and omit any ingredients listed above.
It’s been a game changer for many of our readers.