Once upon a time we had one child and we enrolled him as a toddler in various activity clubs in the area to get him out and socialising with other toddlers and also to get me out and socialising with other mums. I don’t think this is an uncommon thing in modern times. Now we have multiple children and said children are now much older and starting to answer back and the such-like so the clubs have been pared back to the bare essentials for sanity’s sake.
The one thing the children have decided to keep up is a martial art; taekwondo to be more specific. The number of clubs have gone down but the commitment to each has increased plus there is all the necessary regalia one needs to participate in said activity. A few weeks (or possibly months ago) I was informed that two out of the three had all outgrown their sparring kits. Normally, this is solved by a little shuffling down the ranks of clothing and kit but as these two children in particular are the same size, it required purchasing of two kits from new.
After multiple attempts at purchasing these items from new via a superfast online shopping service only to find them too small or not fit for purpose and then having to pay for costly returns, in the end I approached the club where I obtained the required items at much more of a cost but fit for purpose and now all is happy again.
It was with dismay, therefore, that I read an article in the July 2019 edition of Pediatric Dermatology (which mysteriously turned up at my door in January 2020) about a foot allergy to taekwondo shoes.
[Rundle CW, Funk T, Brockman RM. Foot allergic contact dermatitis to mixed dialkyl thioureas. Pediatr Dermatol 2019;36:517-519.]
An allergy to taekwondo shoes?
Well, it’s not an allergy per se to the taekwondo shoes. It was an allergy to mixed dialkyl thioureas.
What are mixed dialkyl thioureas?
Dialkyl thioureas are accelerants. They are made by passing liquid hydrogen sulphide through a bath of calcium cyanamide. The resultant compound is made of hydrogen, oxygen, carbon and sulphur. Mixed dialklyl thioureas (MDTU) refers to the two most prevalent compounds, diethylthiourea and dibutylthiourea.
These are added to namely neoprene rubber to make it more stable and pliable and hence the rubber can be moulded into useful shapes such as wet suits, swimming goggles, waders, the foam insole or tongue cushion of trainers and taekwondo sparring shoes.
[Matthys E, Zahir A, Ehrlich A. Shoe allergic contact dermatitis. Dermatitis. 2014;25:163-171.]
However, they are also used to coat paper to stop it yellowing and hence can be found in the photocopying and photographic industry. MDTU is also found in paint and glue removers, nail polishes, elastic in clothing and flame retardant clothing amongst others.
[Liippo J, Ackermann L, Hasan T et al. Sensitization to thiourea derivatives among Finnish patients with suspected contact dermatitis. Contact Dermatitis. 2010;63:37-41.]
In the house, it may be found in tarnish removers, silver dip and jewellery cleaners. It can be difficult to avoid as there are no tests to confirm the presence of MDTU in consumer items.
It was named the Allergen of the Year in 2009 by the North American Contact Dermatitis Group.
How do I know if I am allergy to dialkyl thioureas?
There would usually be an eczema, ie dry, red, itchy skin in areas of skin that come into contact with the neoprene rubber. The usual place is the feet from footwear, more usually from leaching from foot supports or athletic shoes but hands can also get involved, for example from contact with gloves.
And the treatment?
A careful history is required to suspect MDTU allergy, otherwise the clinical picture would be of just a hand or foot eczema or even psoriasis or a fungal infection. Once MDTU allergy is suspected or if the history is not conclusive, the patient would need skin patch testing to confirm the clinical suspicion or rule out MDTU allergy.
With foot dermatitis, increased moisture can allow easy leaching of the allergen from the shoe and so it is important to keep the feet dry as much as possible, with the wearing and frequent changing of socks. Once the patch tests are positive, avoidance of MDTU is key.
Dr Sandy Flann, Consultant dermatologist.