Hexamethylene diacrylate

Endpoint summary

Additional information

Several case reports and survey are available on positive patch test reactions towards the test substance HDDA and other multifunctional acrylates. With the exceptions of two accidental exposures to almost pure HDDA, data on exposure are limited to a description of the occupation. It can be assumed that workers handling UV/EB (electon beam)-curable coatings or printing inks were possibly exposed to HDDA and other acrylates, while individuals using dental or nail care products most likely came into contact with specific methacrylates, because acrylates are not used in these applications.

In most cases it is unclear, if the allergic reactions detected during patch testing were caused by exposure to HDDA itself or are a cross reaction to similar substances. Additionally, patch testing was performed with several allergens in parallel and led to multiple positive reactions. It has been shown that a strong positive reaction may lead to a false positives result on other patch test sites especially of irritant substances in the same run ("excited skin syndrom", Mitchell, 1997). The proposed mechanism is an induced hyperreactivity of the skin area, which lowers the threshold for irritant reactions. Since HDDA is a skin irritant, this mechanism cannot be excluded as the cause for positive patch test reactions.

The following can be deduced from the available data:

- HDDA is capable of causing allergic dermatitis in humans (supporting the classification as a sensitizer)

- in Sweden, 1 case of an allergic reaction to HDDA was detected in all workers in the UV-cured wood coating industry

- in the US, on average 0.8 cases per year of irritant or allergic reactions (no patch testing performed, so causative agent unknown) were observed per plant working with UV/EB curable inks or coatings

- in total, we found 41 allergic cases since 1977 that might potential be related to HDDA exposure, the true number of patients that really handled HDDA will be significantly lower.

- many of the observed skin reactions were irritant dermatitis rather than allergic dermatitis

- a single exposure to significant amounts of (almost) pure HDDA can be sufficient to cause sensitisation (two reports on accidental exposure)

- skin reactions completely resolved in the course of days to weeks after cessation of contact, partly helped by standard allergic medication

- PPE are efficient to prevent skin reactions and initial sensitisation. Described cases always included frequently soaked clothes and/or no or worng type of gloves worn

Our (the registrants) own records show 13 dermal contacts to HDDA between 1991 and 2003, that caused temporary itching, redness, or papules shortly after exposure due to the irritant properties of HDDA. No signs of allergic reactions were described.

Mitchell (1997): Managing the excited skin syndrome: patch testing hyperirritable skin; Contact Dermatitis 1997, 37, 193 - 199