Is scabies an STI? What scabies is and is not

Is scabies an STI? Not in the classic sense, but it does appear in the Dutch multidisciplinary STI guideline. The reason is simple: the scabies mite passes through prolonged skin-to-skin contact, and sex is a common form of that. Cuddling and sharing a bed count just as much.

That makes scabies a contact infection rather than a venereal disease.

The distinction is not academic. It decides who you need to tell, who gets treated alongside you, and whether an STI test makes any sense at all.

How does scabies spread?

Scabies spreads through direct skin-to-skin contact that lasts long enough. The RIVM LCI guideline uses roughly 15 minutes as a rule of thumb for ordinary scabies. A handshake or a brief hug is therefore almost no risk, while sharing a bed is.

The mite walks slowly and cannot jump.

In ordinary scabies there are usually only 5 to 10 mites on the entire skin. That low number explains why brief contact is rarely enough. In the rare crusted form things are completely different: there can be up to 4,700 mites per gram of skin flake, and then transmission via textiles or even airborne flakes becomes possible.

So why is scabies in the STI guideline?

Scabies is in the STI guideline because people with changing sexual partners have a higher chance of picking it up. Not because the mite is sexual in nature, but because sex happens to be prolonged skin contact. The guideline places it alongside the true STIs for a different reason.

That causes a confusion we see often.

People assume a scabies diagnosis means a partner cheated. It follows in no way. Scabies circulates in student houses, care homes and families entirely independently of sex.

That last row matters most in practice. With scabies you treat the whole household, including people you have never had sex with.

Can you test for scabies?

No, there is no blood test or PCR for scabies. The diagnosis is made by examining the skin, sometimes with a dermatoscope or by putting a skin scraping under a microscope. A laboratory STI test says nothing about the presence of mites.

The same applies to pubic lice.

What is possible, and what the RIVM guideline itself mentions, is to consider STI testing when the infestation was probably acquired through sexual contact carrying STI risk. That is not advice to test, but an observation that the contact overlaps. A test for chlamydia, gonorrhoea and trichomonas measures those three, not the mite.

How do you recognise scabies?

Scabies causes intense itching that is worse at night, with small bumps and sometimes fine burrows a few millimetres long in the skin. Typical sites are between the fingers, the wrists, armpits, navel, groin, penis, and in women the areola. The face is usually spared in adults.

The itch only starts 2 to 6 weeks after transmission.

With a second infestation it goes much faster, sometimes within 1 to 4 days, because your immune system already knows the mite (RIVM). That difference in timeline is often the best clue as to whether this is your first time. If the itch sits in the pubic hair with white dots on the hairs, pubic lice fits better.

How is scabies treated?

Scabies is treated with permethrin cream over the whole body or with ivermectin tablets, and both call for a second round. The Cochrane review found no difference in effectiveness between permethrin and ivermectin after two weeks (Rosumeck et al., 2018). Household members and partners are treated at the same time.

Simultaneous treatment is the entire point.

Treat in turns and you simply hand the mite a fresh host each time. How long you remain contagious after starting is set out in how long is scabies contagious.

What does this mean for you?

If you picked up scabies from someone you also had sex with, that moment of contact overlaps with the route other infections take. It says nothing about blame and nothing about hygiene. It says something about what else could have been passed on in the same period.

We think that is a more honest framing than calling scabies an STI.

The full overview of parasitic skin complaints and what a laboratory can and cannot do with them sits in our main article on pubic lice. Always discuss persistent symptoms with your GP.

References

• RIVM, LCI guideline scabies. lci.rivm.nl
• Rosumeck S, Nast A, Dressler C. Ivermectin and permethrin for treating scabies. Cochrane Database of Systematic Reviews, 2018. PMID 29608022
• Patel PU, Tan A, Levell NJ. A clinical review and history of pubic lice. Clinical and Experimental Dermatology, 2021. PMID 33811771
• Richtlijnendatabase, Multidisciplinary guideline on sexually transmitted infections, scabies module. richtlijnendatabase.nl

Every blood test result includes a professional assessment from a BIG-registered doctor. For treatment decisions, discuss your results with your GP.