How often should you clean pyjamas?

Discussing personal and household hygiene on BBC radio Derby with Andy Twigge.

Here are my notes and sources on the subject – make up your own mind:

  • A complete layer of skin is lost and replaced on average every 4 days
  • We release about a million skin particles a day
  • Skin typically harbours up to 10 million bacteria per cm2
  • Many thousands of bacterial species live on the skin, and a typical person will have about 150 different species on the hands alone
  • Normal skin microbiota are beneficial and we should not seek to eliminate them
  • Clothing typically harbours 100 – 1 million cells per cm2 – they are mostly non-pathogens and not a major problem to most people
  • Clothing acts as a barrier to dispersal
  • Washing clothes regularly is beneficial for lots of reasons not just microbial hygiene
  • Immunocompromised people may be at higher risk
  • Contaminated clothing is relatively low risk for behavioural reasons
  • Hand hygiene is the most important
  • Hand and food contact surfaces are next most important
    1. Kitchen cloths especially – are the biggest reservoir of active bacteria in the whole house, pathogens commonly reside there
  • What is the route by which contaminated clothing could cause illness?
    1. Through contact with skin especially if broken
    2. Through doing the laundry – wash hands
    3. Wet clothing or hands significantly increases the chance of transfer
  • Washing clothes is beneficial by:
    1. Diluting and washing off organisms
    2. Killing organisms which may stay attached
  • Microbes are exchanged between items in the washing machine
  • Higher temperatures and use of bleach in the wash will increase the kill rate
  • Consider also the cost of laundering:
    1. Financial
    2. Environmental (water, electricity, chemicals)
    3. Time


  1. Microbiome analysis and confocal microscopy of used kitchen sponges reveal massive colonization by Acinetobacter, Moraxella and Chryseobacterium species
  2. The influence of sex, handedness, and washing on the diversity of hand surface bacteria
  3. Killing of Fabric-Associated Bacteria in Hospital Laundry by Low-Temperature Washing
  4. Use of quantitative microbial risk assessment for evaluation of the benefits of laundry sanitation
  5. Effectiveness of Low-Temperature Domestic Laundry on the Decontamination of Healthcare Workers’ Uniforms
  6. The-infection-risks-associated-with-clothing-and-household-linens
  7. Cleanliness in context- reconciling hygiene with a modern microbial perspective
  8. The human skin microbiome
  9. Microbial biofilms and the human skin microbiome