Weaning
Starting on solid food can lead to looser stools and a greater likelihood of nappy rash affecting your baby.
Common Cold
When a baby has a cold, stools are often looser, meaning that nappy rash is more likely to occur.
Teething
A runny nose, lots of saliva and diarrhoea are often the signs of teething. It's also a time when nappy rash can strike.
Antibiotics
Nappy rash is often linked to antibiotic use. Antibiotics may mildly upset the digestive system leading to diarrhoea and nappy rash.
1. Morris H, The bottom line on nappy rash, British Journal of Midwifery, Sept 2012, Vol 20, No 9, page 623-626)