What to do if you have a reaction to a cosmetic product


I was disappointed with the way Watchdog handled its coverage of methylisothiazolinone. Quite apart from the blatant sensationalisation and lack of explanation, it also failed to address a pretty key question.  What do you do if you develop a reaction to a cosmetic product?

An allergy is something that any of us  can develop at anytime to anything.  But there are a few things that really seem to cause a lot of skin reactions.  One of the most common is nickel.  This obviously has nothing to do with cosmetics but it is worth pointing out that nobody knows what it is about nickel that makes it so allergenic.  If nickel had just been discovered no chemist would predict that an unusually high number of people would develop red itchy rashes to it.

Nickel allergy means that the sufferer needs to be careful in their choice of jewellery and clothing, but otherwise is not too bad a condition to have.  Food allergies on the other hand can be very serious indeed.  Although the bulk of allergic reactions are relatively mild, there is always the chance of an extreme one which might put you in hospital and very very rarely might kill you.  Nut allergies are something we all know about because activists have persuaded every conceivable source of nut contamination to prominently label the risks.  (At least they have in the UK – You can’t visit a supermarket here without being warned over and again which products might contain nuts.)

In the overall scheme of things allergies to cosmetics are one of the least troublesome manifestations of this problem.  Cosmetics are used in small quantities, and most of what is applied never makes it across the skin.  Formulators have learnt to avoid ingredients that have a tendency to cause lots of allergies.  On top of that there is industry wide co-operation to minimise reactions to known allergens.  (More on that later.)

As a result, the total number of reactions to cosmetics and personal care products is pretty low.  As far as I know there has never been a death due to an allergic reaction to a cosmetic product. It is a theoretical possibility, but has probably never happened.

But while the overall percentage is low, of course if you are one of the unlucky ones who does get a reaction, you are affected 100%.  Knowing you are in a small minority won’t be too much comfort.  So what do you do if you have reaction to a cosmetic product?   Lets look at the science.

Allergic reactions are caused by your immune system identifying something it encounters as a problem.  We all have the potential to develop an allergy to just about anything at just about any time. The most extraordinary example I have heard is Stephen Fry.  He reports that he is allergic to champagne.  He describes being taken to hospital on one occasion and missing a ball as a consequence.  Champagne allergy is a fairly rare one, and unless champagne becomes an item of mass consumption is unlikely to become one.   You need a reasonable level of exposure to the allergen for the allergy to develop.

Another surprising allergy is when the body actually becomes allergic to bits of itself.  This seems to be at last a part of what happens in the case of eczema.  The technical term is autoimmunity.  But back to the skin.

In the case of a skin allergy what happens is that the agent crosses the skin where it encounters the white blood cells.  The white blood cells will latch onto to a particular shape of molecule which they interpret as a threat.  This might not be the whole molecule, it might be a portion of it.  In fact might be the result of a reaction between the allergen and a protein in the skin.  But what happens next is that the body reacts as if it is being attacked by something foreign.  Blood vessels expand to allow the white blood cells easy access to the site of the attack.  This is why the skin goes red – the scientific term is erythema.  Lots of inflammatory agents are released that are intended to destroy the perceived aggressor.  The skin feels hot and itchy in a form of collateral damage.

There isn’t much rhyme or reason to which materials are most likely to cause allergies, but some seem to be a lot more prone to it.  Common causes are preservatives.  Two of the most commonly experienced allergies are to the parabens and methylisothiazolinone/methylchloroisothiazolinone.   This is because these two agents are very widely used.

Paradoxically, they get used widely because they don’t cause many skin reactions.   If you ship millions of units, as big cosmetics companies do, you will get reports back of allergies.  These get taken seriously and if an ingredient is identified that is causing a lot of allergic reactions it gets formulated out.  All the companies end up converging on the same low allergen inducing alternatives – which in practice means the parabens and the azolinones.   This is fine for most of us, but gives the small number of people who are allergic to them a real problem because they have so few alternatives.

Other preservatives, especially the organic acids in my experience, are also quite likely to be culprits.

Here is a list of the most common ones.  They are very very roughly in order of how widely I think they are used.  Do remember that paradoxically you are probably more likely to react to something that is less widely used and lower down the list.  (Fellow formulators are very welcome to dispute my assessments of relative used levels.)

Methylparaben, ethylparaben, propylparaben and butylparaben



Sodium benzoate

Benzoic acid

Dehydroacetic acid

Potassium sorbate

Sorbic acid

Sodium dehydroacetate




DMDM Hydantoin

Benzyl alcohol


Diazolidinyl Urea

Iodopropynyl butylcarbamate

Those are the most commonly used ones.  There are quite a few more that are approved for use but which are so rarely encountered I have kept them off the list, which is probably already too long.

Fatty acids also affect some people in a way that has always seemed very strange to me.  The most common fatty acid involved is stearic acid, but myristic acid, palmitic acid and oleic acid can also cause reactions.  This is strange because these are all commonly found in food and yet I can find no accounts in the literature to people reacting to eating them.  The reaction is also highly dependent on the formulation, making it a hard one to track down.

Food colourings are controversial and luckily I don’t have to get into that here.  But colourings in cosmetics very very rarely cause any allergic reactions, so that at least can be ignored.

Fragrances and essential oils are typically packed full of components that have form as allergens.  This fact has been recognised in the EU legislation which requires the 26 most commonly encountered allergens to be specifically listed.  This is a good pragmatic approach because both fragrance and essential oils can possess quite a lot components and it would quickly become impossible for them all to be listed on the ingredient lists.

You will see these fragrance allergens on any number of products.  But in fact allergies to these are not all that commonly encountered.  The reason for this is that there is a code of practice controlled by an organisation called IFRA- the International Fragrance Research Organisation – which publishes and continually updates guidelines on how to formulate fragrances.  These aren’t compulsory but almost every significant company follows them.  This is one of the cosmetic industries best kept secrets, and it is a shame that more people don’t know about it.  I may do a blog post on it in the future.

But even so, the list of allergens is worth referring to if you have experienced a reaction.

Here is the list in full.

Amyl Cinnamal

Benzyl Alcohol

Cinnamyl Alcohol





Amcylcinnamyl Alcohol

Benzyl Salicylate




Hydroxyisohexyl-3-Cyclohexene Carboxaldehyde

Anise Alcohol

Benzyl Cinnamate


Butylphenyl Methylpropional


Benzyl Benzoate


Hexyl Cinnamal



Alpha-Isomethyl Ionone

Evernia Prunastri Extract

Evernia Furfuracea Extract

So you now have a list, probably slightly longer than you wanted, of potential allergens in the cosmetic product you are having issues with.  You might now be able to spot the ingredient that is giving you trouble just from comparing the lists of products which give the problem and those that don’t.

A few points though – although very low levels of an allergen can provoke a reaction there is still a minimum level that is needed.  If an ingredient is present on a pack list, it might well be there in vanishingly small quantities.  So even if you discover you are allergic to say limonene you might well find that not every product that contains limonene is an issue.

Also different formulations affect the way things work.  I am sensitive to potassium sorbate myself for example.  But only to a relatively high level – higher than is normally used – and only in certain formulation types.  At normal use levels in a skin cream I am fine with it.  In fact if it weren’t for my job I would never have known.

So if you are trying to pin down the cause of your problem do bear in mind that it may not be completely straight forward to get to the bottom of the problem.   One thing that can help is going to a doctor and asking for a patch test.  This involves deliberately applying small quantities of known allergens to patches of skin on the back.  This is a standardised test which allows dermatologists to compare their data with each other.

Like any other test, particularly biological ones, you need to bear in mind that it has some shortcomings.  For a start the ingredients are added on their own, so you miss out on interactions between the ingredient and the formulation.  They are also applied at levels higher than they are normally used.   These shortcomings are inevitable given what the patch test is trying to achieve, but they are worth bearing in mind.  For example if I was patch tested I would no doubt show up as sensitive to potassium sorbate, even though I know that there isn’t a product on the market that I couldn’t tolerate.

The patch test protocol makes false positives more likely – quite rightly – but it can also give a false negative.  It is possible that the allergic reaction will only occur in the presence of another agent that encourages it to be absorbed across the skin.  The skin is in general a good barrier but there are exceptions.  Quite a few of the fragrance allergens for example will readily cross the skin and might well do it even more efficiently if they have been solubilised.

So if you are unlucky enough to suffer from an allergic reaction I hope this has helped with your detective work.  I’d love to hear of any experiences you may have had that might help other sufferers.  And if you haven’t had any trouble with allergies yet, don’t feel too smug about it.  It is something that can develop more or less any time and there is no way of knowing when.

So whether or not you have an allergy, Good Luck!

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