Skip to Content

What kills lice cold or hot water?

Quick Answer

Both hot and cold water can be effective at killing lice. Hot water over 130°F can kill lice and their eggs quickly, while prolonged exposure to cold water can also be lethal. However, there are some advantages and disadvantages to each method. Hot water can be more effective at penetrating the lice’s waxy exoskeleton and destroying the eggs, but it carries a safety risk if the water is too hot. Cold water may take longer but is safer. The most important factor is ensuring thorough and prolonged contact with the water regardless of temperature.

Does Hot or Cold Water Kill Lice Better?

Hot water is generally considered more effective at killing lice for a few key reasons:

  • Hot water above 130°F can quickly kill lice and their eggs by denaturing proteins and melting the wax on the lice’s exoskeleton.
  • The high temperature helps the water penetrate deep into the lice’s protective outer coating.
  • Hot water can kill lice and eggs in under 10 minutes, while cold water may take an hour or longer of exposure.

However, there are some advantages to using cold water as well:

  • Prolonged exposure to very cold water below 55°F can still be lethal to lice, it just takes longer.
  • Cold water poses no safety risks like scalding or burns.
  • Some research suggests cold water makes it harder for lice to hold onto hair shafts.
  • The cold causes lice to become immobile and fall off hair more easily.

So while hot water may kill lice more quickly, cold water can also be effective if exposure is long enough. The most important factor is ensuring the lice and eggs are thoroughly saturated and exposed to the water for an extended period regardless of the temperature.

Hot Water Treatment

Hot water is one of the most traditional and effective home remedies for killing head lice. Here are some key considerations:

  • The water should be at least 130°F to kill lice and their eggs quickly, but ensure it’s not so hot as to scald the scalp.
  • Wet the entire head of hair thoroughly and work the hot water down to the roots.
  • It may help to use a showerhead on a high setting to penetrate the hair better.
  • Soak the hair for at least 10 minutes, up to 30 minutes, to kill all lice.
  • Repeat the hot water treatment every 3-4 days for 2 weeks to kill newly hatched lice.
  • Comb out the hair with a nit comb while washing to help remove dead lice and eggs.

Hot water on its own may not be 100% effective at removing all traces of lice. Combining it with combing, medicated shampoos, or suffocation-based treatments can improve results.

Safety Precautions

Take care to test the water temperature before treating children to avoid scalding. Also, limit hot water exposure on color-treated or chemically processed hair.

Cold Water Treatment

While not as fast acting as hot water, prolonged exposure to very cold water can also kill lice in some cases. Here are some tips:

  • The water should be cold, generally below 55°F, but not freezing.
  • Thoroughly soak the head and hair for an extended period, ideally 60 minutes or more.
  • Some sources recommend leaving hair saturated overnight in cold water.
  • Repeat every 3-4 days for 2 weeks to target newly hatching lice.
  • Combing out the hair during the process can help dislodge and remove lice.

The cold temperature makes it difficult for lice to hold onto hair shafts and can immobilize them. Over time, it causes fatal damage. But results may take longer than hot water treatments.

Other Home Remedies

While hot or cold water can kill lice, they may work better when combined with other home treatments. Some options include:

  • Suffocation-based oils – Coating the hair in oils like olive, coconut, mayonnaise, or petroleum jelly can smother lice and eggs and make water penetration better.
  • Tea tree oil – Shampoos or rinses with diluted tea tree oil can kill lice with prolonged contact.
  • Combs – Nit combs can help remove lice and eggs during the wash process.
  • Vinegar – White vinegar helps dissolve the exoskeleton of lice.
  • Salt – Mixing table salt into hot water can improve the water’s insecticidal properties.

Combining these home treatments with hot or cold water submersion improves results by attacking lice in multiple ways. But be wary of overusing chemical treatments or combining too many methods, which can damage hair.

When to See a Doctor

Home remedies are often effective for mild lice infestations. But in severe cases, or if lice persist after thorough home treatment, seeing a doctor may help. Prescription medicated rinses, oral medication, or stronger shampoos may be required.

Signs an infestation may require medical treatment include:

  • Lice or eggs remain after two weeks of diligent home treatment.
  • Severe itching and skin irritation from bites.
  • Sores or bacterial infection from scratching.
  • Difficulty sleeping from itchiness.
  • Self-isolation or social issues resulting from embarrassment.

Doctors can assess the severity of an infestation and prescribe stronger pediculicides or Lindane shampoos to help when over-the-counter options fail.

Prevention Tips

Preventing lice from taking hold in the first place is the best approach. Recommended prevention measures include:

  • Avoid head-to-head contact with anyone who has lice.
  • Don’t share hats, helmets, hair accessories, towels, or brushes with others.
  • Check children’s hair regularly for signs of lice.
  • Keep long hair tied up or braided at school.
  • Use lice-repellent sprays or shampoos periodically.
  • Clean bedding and clothes after a lice exposure.
  • Soak combs and brushes in hot water between uses.

Catching infestations early and treating all close contacts can also prevent transmission and reinfestation.

The Takeaway

Both hot and cold water can be effective home remedies for killing lice when used properly. Hot water may kill lice faster, but cold water is safer. Regardless of temperature, it’s important to saturate the hair fully and comb thoroughly. Combining water treatments with oils, vinegar, and nit combing improves results. See a doctor for prescription solutions if home methods fail. Staying vigilant about prevention is key to keeping lice under control.