Infestations are not merely unpleasant. In crowded conditions with reduced washing, they spread fast, they cause sleeplessness and scratching, scratching causes infected skin, and one of them historically killed more people than the wars it accompanied.
They are also entirely beatable with heat, and the temperature is a real specification rather than a rough idea.
Why this matters more in a crisis
Every factor that drives infestation gets worse in the scenario this app covers:
- More people sleeping in fewer rooms, which is the correct warmth strategy and the perfect transmission environment.
- Less frequent washing of bodies, clothes and bedding, because water and fuel are rationed.
- Cold washes, because heating water is expensive.
- Shared bedding and clothing.
- Reduced access to treatments from a pharmacy.
- Scratching plus poor hygiene, which turns an itch into a skin infection and, occasionally, into sepsis.
The number that decides it
Head lice
Common, harmless, and not a sign of poor hygiene. They prefer clean hair.
Signs: itching, especially behind the ears and at the nape; live lice visible; eggs (nits) glued firmly to hair shafts near the scalp. Nits that come off easily are usually dandruff.
Detection combing is how you diagnose it. Wet the hair, add conditioner, and comb systematically from the scalp outward with a fine-toothed detection comb, wiping the comb on kitchen paper after each stroke. This is more reliable than looking.
Wet combing treatment, which needs no chemicals and works if done properly:
- Wash the hair, apply plenty of conditioner, leave wet.
- Comb the entire head thoroughly with a fine detection comb, section by section.
- Rinse the comb constantly.
- Repeat on days 1, 5, 9 and 13. That schedule is what matters: it catches lice hatching from eggs the earlier combs missed, before they mature enough to lay.
- Check again on day 17.
Missing the repeat combs is why it fails. A single session removes lice and leaves the eggs.
Chemical treatments work but resistance is widespread, and dimeticone-based products (which suffocate rather than poison) are generally more effective than older insecticides. Two applications a week apart.
Check everyone in the household on the same day, and treat only those who actually have live lice.
Scabies
A mite that burrows into the skin. Far more uncomfortable than lice and it needs whole-household treatment.
Signs: intense itching, dramatically worse at night; a rash of tiny red bumps; thin silvery burrow lines, most often between the fingers, at the wrists, elbows, armpits, waistband, buttocks and genitals. In babies and small children it also affects the palms, soles, face and scalp.
The itch can take 4 to 6 weeks to appear after infestation, which is why it spreads through a household before anyone knows, and why everyone is treated at once regardless of symptoms.
Treatment:
- Permethrin 5% cream is the usual first line. Applied to the whole body from the neck down, including between fingers and toes, under nails, and the genitals. For babies, young children and the elderly, include the scalp, face and ears.
- Leave it on for 8 to 12 hours, so overnight, then wash off.
- Repeat after 7 days, without fail. The second application kills mites that hatched from eggs after the first.
- Treat every member of the household on the same day, and any close contacts, whether or not they itch.
- Wash all bedding and clothing in the house at 60°C or higher on the first day of treatment, and hot tumble dry.
- Bag anything unwashable for 72 hours.
Body lice, which are the dangerous ones
Distinct from head lice, and the reason this page is not merely about discomfort.
Body lice live in clothing, not on the body, coming to the skin only to feed. They are associated specifically with people who cannot change or wash clothes: crowded conditions, cold weather, displacement, and exactly the circumstances a prolonged emergency creates.
They transmit disease. Epidemic typhus, trench fever and relapsing fever are all body-louse-borne, and typhus has historically killed on a scale comparable to the wars and famines it followed. This is not a historical curiosity: it reappears wherever people are cold, crowded and unable to wash.
Treatment is the clothing, not the person. Wash and hot-dry everything at 60°C or higher, or replace it. Regular bathing and a change of clothes eliminate them.
This is the strongest hygiene argument in the app: keeping a way to wash clothes hot is not a comfort measure in a long emergency, it is disease control. See washing clothes without power.
Bedbugs
Not a health risk in the disease sense, and a serious quality-of-life problem, because they destroy sleep and sleep deprivation degrades every decision a household makes.
Signs: rows or clusters of itchy bites, often on skin exposed while sleeping; small blood spots on sheets; dark specks of droppings along mattress seams and bed frames; a sweetish musty smell in a heavy infestation.
They are very hard to eradicate and very good at hiding, surviving months without feeding.
Heat is the answer here too:
- Wash and hot-dry all bedding and affected clothing at 60°C or higher.
- A hot tumble dryer for 30 minutes kills all stages, including eggs, and works for items that cannot be washed.
- Vacuum thoroughly, seams and crevices included, and dispose of the bag outside immediately.
- Steam clean mattresses and frames if you can.
- Bag and isolate anything you cannot treat.
- Pull beds away from walls, remove clutter, and consider mattress encasements.
In hot weather, a sealed black bag left in direct sun can reach lethal temperatures, which is a genuinely useful no-power option in a British summer.
The heat treatment without a washing machine
The practical problem in a power cut, and the reason this section exists.
- Boil the laundry. A large pot over a fire, held at a simmer for 10 to 15 minutes, comfortably exceeds every temperature on this page. This is how it was done for centuries and it is completely effective.
- A haybox will hold laundry above 50°C for a long time after a short boil, which turns a fuel-expensive job into a cheap one. Bring the water and the fabric to the boil, then insulate it for a few hours.
- A solar oven or a car in summer will reach lethal temperatures for bagged items.
- Bagging for 72 hours costs nothing at all and handles anything that cannot take heat.
- Freezing works too where it is genuinely cold: several days below freezing kills most of these, and a British winter outbuilding may do it.