Chemical of the Month: Formaldehyde

By Toxicologist Ewa Daniel  

What is it

Formaldehyde is a chemical that can be found both in nature and most living systems including humans as well as found synthetic made as an aqueous solution. It can be used in many different types of products from paint, impregnation agents, glue, coating, fillers, plasters, modeling clay, polymers, biocides and polish to cosmetics such as cream, shampoo, balsam, soap, hand disinfectants and household products; detergents, cleaning products. Formaldehyde is present in both indoor and outdoor air at low levels, usually less than 0.03 parts of formaldehyde per million parts of air (ppm).

In cosmetics and household products formaldehyde is usually added to the products as a preservative in order to avoid bacteria and fungus. But it can also be found in the products as an impurity released from other chemicals that have been added the product.  The chemicals are called formaldehyde releasers or donors and they will release formaldehyde in the presence of water.

So, what is the problem

Formaldehyde is a common cause of skin allergy. European studies show that 2-3 % of skin allergy patients are allergic to formaldehyde. In the US it is even worse with 8-9 % of the patients having allergy to this chemical. Allergy to formaldehyde can be very difficult to deal with, since it is not just formaldehyde that you need to avoid.

This is because some people will not only react to formaldehyde, but also to formaldehyde releasers and so far, it is found that more than 30 chemicals can release formaldehyde. In cosmetics there are 11 well known formaldehyde releasers that are able to cause allergic reaction, and in industrial products it is even more difficult since they can all have different names.

Formaldehyde releasers that can be found in cosmetics:

  • Benzylhemiformal
  • 2-bromo-2-nitropropane-1,3-diol
  • 5-bromo-5-nitro-1,3-dioxane
  • Diazolidinyl urea
  • DMDM hydantoin
  • Formaldehyde
  • Imidazolidinyl urea
  • Methenamine
  • Paraformaldehyde
  • Sodium hydroxymethylglycinate
  • Quaternium-15

In Industrial product the formaldehyde releaser can have many different names:

  • 2-Bromo-2-nitropropane-1,3-diol
  • 5-Bromo-5-nitro-1,3-dioxane
  • Benzylhemiformal
  • Brom-nitro-dioxan
  • Brom-nitro-propandiol
  • Bronidox
  • Bronopol
  • Chloroallyhexaminiumchlorid
  • Diazolidinyl urea
  • Dimethylol urea
  • Dimethylhydantoin formaldehyd resin
  • Dimethylol-dimethylhydantoin
  • Dimethylurea
  • DMHF
  • DMDM hydantoin
  • Dowicil 200
  • Dowicil 75
  • Euxyl K 200
  • Formaldehyde
  • Formalin
  • Germall II
  • Germall 115
  • Grotan BK
  • Hexamethylentetramin
  • Hexamine
  • Imidazolidinyl urea
  • MDM hydantoin
  • Methenamin
  • Monomethylol-dimethylhydantoin
  • N-methylol-chloracetamid
  • N-methylolethanolamin
  • Parmetol K50
  • Paraformaldehyde
  • Polyoxymethylen
  • Preventol D2
  • Quaternium-15
  • Sodium hydroxymethylglycinate
  • Trihydroxyethylhexahydrotriazin


Skin allergy is concentration depended. This means that the higher a concentration you get exposed to, the higher risk for an allergic reaction. This also means that you won’t always have an allergic reaction to the chemical you are allergic to, simply because; if the concentration is low enough you might be exposed to the chemical without an allergic reaction. An example is nickel: many studies have shown that most people with allergy to nickel can be exposed to very low concentrations of nickel (10 ppm) without having an allergic reaction. It is the same with formaldehyde.

In a Danish study 20 patients allergic to formaldehyde were exposed to a serial dilution of 25, 50, 250, 500, 5000 and 10 000 ppm formaldehyde aqua. All 20 reacted in a concentration at 10 000 ppm, 9 out of 20 to 5000 ppm, 3 out of 20 to 1000 ppm, 2 had a positive reaction down to 500 ppm and only 1 patient was positive to 250 ppm formaldehyde. A retest of the the patient reacting to 250 ppm 1 year later with 50, 100 and 250 ppm showed a negative reaction (no reaction) on all three concentration. Based on this the threshold concentration for formaldehyde patients was set to 250ppm.

More important than the threshold for positive patch test responses is to determine which concentrations of formaldehyde may cause eczematous reactions when products containing  formaldehyde are applied under normal use conditions.  In another study on 11 formaldehyde-sensitive patients it was concluded that formaldehyde levels below 30 ppm can be tolerated by most sensitive subjects if continually applied to sensitive areas like the axilla.    


Formaldehyde can have many side effects such as being allergenic and toxic in skin contact, and cause cancer when people are exposed in high concentrations. Because of that producers are not allowed to use formaldehyde or formaldehyde donors as preservatives in AllergyCertified products.

But it is impossible to avoid formaldehyde completely since it is found in the air around us and many products produce formaldehyde on their own. As an impurity AllergyCertified can allow up to 10ppm, this concentration is below the safe threshold and even people with allergy to formaldehyde should be able to use the products without having an allergic reaction or other side effects.

AllergyCertifieds toxicologist always look for formaldehyde during the risk assessment made in the certification process and sample test for formaldehyde are in order to make sure that the producers comply with this demand.


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