Wikipedia:Reference desk/Archives/Science/2020 February 1

= February 1 =

Hydrogen peroxide and white fingers
Goodmorning. Why the common disinfectant hydrogen peroxide 3% make temporarily the fingers white? What happened in our skin, is it a chemical reaction?

Thank you very much for the attention--87.7.92.114 (talk) 12:11, 1 February 2020 (UTC)
 * This is complicated, as a lot depends on the concentration, the exposure time and the state of the skin (oily skin resists better).
 * Hydrogen peroxide is a powerful oxidiser, even in a weak 3% solution. It has several effects, some of which aren't oxidation. It also acts as a dewatering agent (water in a substance will preferentially bond to the H2O2, rather than the previous substance). Much of the oxidation is seen as a 'bleaching' effect.
 * By 'skin' here, you may mean the epidermis of the skin, rather than the dermis beneath. This is sometimes described as a 'dead' layer, but that's wrong - what it means is that there's no blood supply within it (the dermis has a blood supply), and the layer must be nourished just by permeability through it. The very outer layer of this is the stratum corneum, made of corneocytes - skin cells which have lost much of their normal cell contents and have also become keratinised (I'm simplifying a lot). They do though still contain a lot of water (if they lose this, you get dry, cracked skin).
 * Many substances, including skin, are transparent in close up, because they are water-filled cells which have a similar refractive index all the way through. There are many cell boundaries, but these aren't visible. Microscopy might need to use phase-contrast microscopy to see them. If they lose this consistency though, they stop being transparent and become translucent or opaque, usually white (there's nothing to colour them) because light can no longer pass through an optically consistent medium, but it starts to get scattered on the boundaries. Physically, the first effect we see from weak hydrogen peroxide on clean skin is no more than a dewatering effect. Just like dry skin otherwise, the epidermis now becomes white and opaque.  If you expose skin in some places (the palms, finger tip pads, or sometimes the soles of the feet), that skin also has a layer, the stratum lucidum, beneath the corneum which displays this effect even more obviously.   This effect is mostly reversible with a skin moisturiser, or just washing with water.  The effect here is mostly physical, rather than a chemical reaction  (it's removing free water, not reacting with the skin).
 * If you have a longer exposure, more concentrated hydrogen peroxide, or a deeper exposure (such as an abraded or cut surface) then you might see its effects on the dermis. The effects here can start to become more serious, especially if the peroxide is concentrated. it may cause permanent effects (which may heal over time, or may even form permanent scars, like a burn). 30% peroxide (hairdresser grade) is enough to do this. The physical effects can be supplanted by real chemistry.  Anything which involves oxidation within the dermis counts as a chemical burn, won't be reversible within minutes and would need to heal long-term, if it can.
 * It can be nasty stuff, if you go over the 3% region! Andy Dingley (talk) 14:41, 1 February 2020 (UTC)


 * "Many workers have noted that inadvertent skin contact to the more concentrated solutions [of hydrogen peroxide] causes white spots which spontaneously disappear within some hours; the change of colour is due to formation of oxygen microbubbles in the skin".  Alansplodge (talk) 14:46, 1 February 2020 (UTC)
 * I've had this happen to me (with 50%). But in terms of WP and RS, Hydrogen peroxide concurs. Its cited website sounds more WP:SECONDARY than the case study you mention, but the archived content of its link does not mention this idea and the current target of the link only goes to a list of documents (uncertain which if any would be relevant). Seems like a ripe chance for WP:RD to lead to an article improvement:) DMacks (talk) 19:03, 2 February 2020 (UTC)

diagnosed without symptoms
I don't understand. "A 10-year old boy was diagnosed with the coronavirus despite showing no symptoms." How could the "10-year old boy [be] diagnosed with the coronavirus despite showing no symptoms"? Bus stop (talk) 18:44, 1 February 2020 (UTC)
 * More detail. He was tested because his relatives showed symptoms. --Wrongfilter (talk) 19:13, 1 February 2020 (UTC)
 * "The 10-year-old boy’s lungs were also scanned 'on the insistence by the nervous parents' and showed signs of infection, which was confirmed by swabs of the back of his nose and throat. That meant he was capable of transmitting the virus even though the kind of tests used in airport screening for the virus would not identify him as a carrier." So then why is a 14-day quarantine necessary for all Americans traveling from Wuhan to the US, beginning February 2 2020 at 5 pm eastern time? If there is a test—lung scans plus swabs of the nose and throat—wouldn't that obviate the need for all travelers to be quarantined? ("The United States government declares a public health emergency due to the coronavirus, and is closing its borders to all foreign nationals 'who pose a threat of transmitting the virus from entering the country and would quarantine U.S. citizens returning from Hubei province in China, the epicenter of the outbreak, for up to 14 days,' starting Sunday, Feb. 2 at 5 p.m." ) Bus stop (talk) 19:27, 1 February 2020 (UTC)
 * The test would obviate the need for a quarantine only if it were (close to) 100 per cent reliable and never showed any false negative. Presumably that is not the case. --Wrongfilter (talk) 19:42, 1 February 2020 (UTC)
 * "Presumably" that is ruling out governmental overreach. Bus stop (talk) 19:44, 1 February 2020 (UTC)
 * Better safe than sorry. ←Baseball Bugs What's up, Doc? carrots→ 19:56, 1 February 2020 (UTC)

Symptoms = coughing, fever, that sort of thing. Test positive = the virus is detected by a throat culture, blood test, or whatever, showing that the person is infected. Incubation period = time between infection and when symptoms appear. For coronavirus this appears to be around 5 days according to news reports I saw yesterday. For HIV it can be months or maybe years before seroconversion. There isn't any contradiction between being infected and not showing symptoms. Just like there is no contradiction between a fire in your house (a cigarette butt is smouldering in the wastebasket) and it not yet being big enough to see flames coming out the windows from outside. 2601:648:8202:96B0:0:0:0:E118 (talk) 01:31, 2 February 2020 (UTC)


 * I asked How could the "10-year old boy [be] diagnosed with the coronavirus despite showing no symptoms"? but I didn't say there was a "contradiction". Bus stop (talk) 01:43, 2 February 2020 (UTC)
 * "I don't understand" followed by the question "How could" is an expression of incredulity and a disbelief in the veracity of the statement in question. The response to your expression of incredulity and disbelief should take into account that tone.  -- Jayron 32 16:08, 6 February 2020 (UTC)


 * I agree 100% that there isn't any contradiction between being infected and not showing symptoms. This should be obvious. In my haste to inquire into systems in place at various sorts of settings ranging from airports to hospitals I might have given the misimpression that I doubted that infection could be present in the absence of symptoms. I was just clarifying that I didn't say there was a contradiction. If my "tone" was inappropriate, I apologize. I probably should have given my response more consideration prior to posting it. Anyway, I sincerely appreciate the response of 2601:648:8202:96B0:0:0:0:E118. Bus stop (talk) 17:40, 6 February 2020 (UTC)


 * Also I thank you Jayron32 for raising this question. I welcome the opportunity to clarify what I think I was trying to say. Clearly 2601:648:8202:96B0:0:0:0:E118 knows more about this subject than I do. I for instance have the feeblest grasp of Seroconversion, linked to by 2601:648:8202:96B0:0:0:0:E118. I also would not want to be responsible for misleading onlookers into thinking the medical problem of coronavirus can not be present if no symptoms are seen. Sadly, a doctor in China considered one of the first to identify the 2019–20 Wuhan coronavirus outbreak has died. His name was Li Wenliang. Bus stop (talk) 05:39, 7 February 2020 (UTC)


 * There are lots of ways to do diagnostics. I was recently diagnosed with strep even though I didn't have a sore through a rapid test. My wife had a rapid influenza A test positive, even though her symptoms didn't match standard flu. In both cases, we had rapid antigen tests. There are also antibody tests, and various forms of nucleic acid tests, such as PCR. None of these tests require the expression of standard symptoms (or symptoms at all) for positive diagnosis of infection, including viral. According to the CDC, coronavirus testing is currently a form of nucleic acid test called a Real-Time PCR test. This essentially confirms the presence of coronavirus by detecting its genome within a sample. This is a pretty accurate methodology, and as with all NAT testing, is not at all dependent upon symptom expression. --OuroborosCobra (talk) 01:52, 2 February 2020 (UTC)


 * If it is a "a pretty accurate methodology" why quarantine people for 14 days? Bus stop (talk) 02:00, 2 February 2020 (UTC)
 * It depends what "pretty accurate" means. ←Baseball Bugs What's up, Doc? carrots→ 08:36, 2 February 2020 (UTC)
 * Well, first off, you need quarantine for those that test positive. The 10-year old you started this conversation about tested positive even though they were asymptomatic. That would seem to be the point, we cannot quarantine based just on symptom expression or field tests at airports. RT-PCR is an intensive lab based testing technique and cannot be done at airports as passengers come off of planes. It can take hours or even days to get results. If we wait for the RT-PCR result before doing a quarantine, we are going to lose people to the general population and expose people in the general population while waiting for a test result. That doesn't sound terribly effective to me. Additionally, while NAT techniques are generally quite accurate, that accuracy is dependent upon access to genetic primers for the testing, and the quality of those primers. They need to be unique enough that non-coronavirus DNA sequences won't give a false positive, but generalized enough that small mutations in coronavirus won't result in false negatives. This actually isn't as easy as it sounds. The way to reduce the chance of mutations resulting in primers not working is to use conserved sequences of DNA, or, sequences that are so vital for function that small mutations generally result in organism non-viability and death, and so natural selection tends to preserve the conserved sections of DNA. This is a double-edged sword, however. Use a conserved genome for, say, an enzyme that is part of the citric acid in one bacteria, and you may find that your primer gives you false-positives for almost any bacteria outside of e Coli. It is not a simple task to find a primer that is both generalized and unique enough for NAT testing. We are dealing with a 2-month old outbreak, so the quality of our primers (we hope) is good enough, but with this short a time for testing, we have to be open to the possibility that our NAT testing method is currently insufficient. --OuroborosCobra (talk) 18:09, 2 February 2020 (UTC)
 * Maybe it's also worth remembering that while the time between exposure and when the virus can be reliably detected with RT-PCR is likely to be shorter than when symptoms show, it's not going to be instantaneous either. So if you concerned the people might have been exposed a few hours ago, you're still likely to want quarantines even if you had a test which gave instant results. (If you're concerned because someone just came from China and you fear they could have been exposed somewhere in China these concerns may apply up until their flight, and probably even on their flight.) And given our current state of knowledge of the virus, any estimates of when you can expect reliable detection are likely to be on the conservative side. Also, while I think testing facilities in most developed countries aren't stretched at the moment, they may not be able to easily cope with a significant increase. And even if they could, you may still want to consider the utility of who you choose to test. Remembering also that for the reasons mentioned before, you're probably going to need to collect specimens from people while they are self-quarantined, rather than simply at the airport or whatever. (While the techniques are something quite a few labs could perform, the number you trust to do it is often small, e.g. in the US it's only CDC Atlanta [//www.cdc.gov/coronavirus/2019-ncov/lab/guidelines-clinical-specimens.html] [//www.cdc.gov/coronavirus/2019-ncov/lab/rt-pcr-detection-instructions.html]. In the event of a nationwide outbreak, together will likely need significant testing capability but this doesn't mean it makes sense to start doing it already, instead of just planning and preparing.) Self quarantine may be somewhat disruptive to the people affected, but it may very well be that doing 14 days of self-quarantine rather than 5 days (random estimate) but with all the costs for testing etc is seen as the best solution. (In the US, I've seen reports the self-quarantine will be 'monitored' [//www.whitehouse.gov/briefings-statements/press-briefing-members-presidents-coronavirus-task-force/] but I'm not sure if this means people visiting, it may simply be phone calls etc with visits only if there are concerns.) Nil Einne (talk) 02:06, 3 February 2020 (UTC)
 * Here's an interview with a virologist some might find informative. One point they make is that self-reporting of symptoms is far from 100% reliable. Mild symptoms especially can easily be ignored or assumed to be from allergies, lack of sleep, etc. --47.146.63.87 (talk) 09:39, 2 February 2020 (UTC)
 * This YouTube video, presented by a doctor, is pretty informative, in my opinion, and it is current as of February 3, 2020. Bus stop (talk) 05:31, 4 February 2020 (UTC)