Mixed Dialkyl Thioureas
The neoprene rubber chemical — why a wetsuit, a knee brace, or a phone case can leave a rash where it touches
INCIMixed Dialkyl Thioureas
- Category
- Rubber_accelerator
- Risk level
- medium
- The neoprene allergen
- Thioureas are characteristic of neoprene (polychloroprene), not natural latex — so you can tolerate latex gloves yet react to neoprene, and vice versa
- Pattern is the clue
- The rash maps precisely to the neoprene item — a wetsuit outline, a brace footprint, a strap line
- What's in the mix
- Mainly dibutylthiourea (DBTU) and diethylthiourea (DETU) as the test allergens
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Commonly found in
Possible reactions
- A rash exactly where a neoprene item presses on skin
- Wetsuit-pattern dermatitis on torso, arms, and legs
- Dermatitis under a knee, ankle, or back brace
- Rash from neoprene sleeves, straps, or compression wear
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What is mixed dialkyl thioureas?
Mixed dialkyl thioureas is a patch-test mixture of two rubber accelerators — chiefly dibutylthiourea (DBTU) and diethylthiourea (DETU) — from the thiourea chemical family. Their defining feature is which rubber they're used in: neoprene (polychloroprene), the material of wetsuits, knee and ankle braces, orthopaedic compression supports, dive gloves, neoprene laptop sleeves and phone cases.
That's the clinically useful distinction. Thiurams and carbamates dominate natural-latex products; thioureas dominate neoprene. So someone allergic to thioureas may wear latex gloves without trouble yet break out under a wetsuit or a brace — and someone with a latex-rubber allergy may be fine with neoprene. Knowing which rubber you react to narrows the search dramatically.
Why it causes reactions
The thiourea group (–NH–CS–NH–) is reactive toward skin proteins, forming the hapten-protein conjugates that drive Type IV delayed hypersensitivity. The presentations are distinctive because they trace the offending object:
- Wetsuit pattern — divers and surfers get dermatitis on the torso, upper arms and legs, mirroring the suit.
- Brace pattern — a rash precisely under a neoprene knee, ankle, wrist or back support.
- Occupational — workers manufacturing neoprene goods can be sensitised on the job.
What I find genuinely useful here is how locatable this allergen is. A rash that stops at the exact edge of a brace or wetsuit is practically pointing at the cause. You don't always need a lab to form a strong suspicion — you need to notice that the rash and the neoprene share an outline. The patch test then confirms it. — Snehal
Where it's found
- Neoprene wetsuits and dive gear — the classic recreational source.
- Orthopaedic and athletic supports — knee, ankle, wrist, back braces.
- Compression sportswear — some high-performance garments.
- Everyday neoprene goods — laptop sleeves, phone/tablet cases, can koozies, some shoe components.
How to spot it
- Match the rash to the neoprene item's footprint.
- Note clearing when the garment or brace is removed.
- Patch test with DBTU and DETU to confirm.
Safer alternatives
- Neoprene-free braces — cotton, polyester, or silicone construction (confirm with the maker).
- Silicone supports — no rubber accelerators at all.
- Cotton barrier liner — a tube sock or sleeve under any neoprene support.
- Skin-friendly or accelerator-free wetsuits from specialist manufacturers.
The bottom line
Mixed dialkyl thioureas are the rubber chemicals of neoprene — distinct from the latex accelerators — so they explain the puzzle of "fine with latex gloves, but neoprene gives me a rash." The tell is a dermatitis that traces the exact shape of a wetsuit, brace, or sleeve. Switch to neoprene-free or barrier-lined gear, and patch test with DBTU/DETU to lock down the diagnosis.
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