Phototherapy is treatment with a special type of light (not sunlight).
It's sometimes used to treat newborn jaundice by lowering the bilirubin levels in your baby's blood through a process called photo-oxidation.
Photo-oxidation adds oxygen to the bilirubin so it dissolves easily in water. This makes it easier for your baby's liver to break down and remove the bilirubin from their blood.
There are 2 main types of phototherapy.
Conventional phototherapy – where your baby is laid under a halogen or fluorescent lamp with their eyes covered.
Fibreoptic phototherapy – where your baby lies on a blanket that incorporates fibreoptic cables; light travels through the fibreoptic cables and shines on to your baby's back
In both methods of phototherapy, the aim is to expose your baby's skin to as much light as possible.
In most cases, conventional phototherapy is usually tried first, although fibreoptic phototherapy may be used if your baby was born prematurely.
These types of phototherapy will usually be stopped for 30 minutes every 3 to 4 hours so you can feed your baby, change their nappy and give them a cuddle.
If your baby's jaundice doesn't improve after conventional or fibreoptic phototherapy, continuous multiple phototherapy may be offered.
This involves using more than one light and often a fibreoptic blanket at the same time.
Treatment won't be stopped during continuous multiple phototherapy.
Instead, milk expressed from your breasts in advance may be given through a tube into your baby's stomach, or fluids may be given into one of their veins (intravenously).
During phototherapy, you baby's temperature will be monitored to ensure they're not getting too hot, and they'll be checked for signs of dehydration.
Intravenous fluids may be needed if your baby is becoming dehydrated and they aren't able to drink a sufficient amount.
The bilirubin levels will be tested every 4 to 6 hours after phototherapy has started to check if the treatment is working.
Once your baby's bilirubin levels have stabilised or started to fall, they'll be checked every 6 to 12 hours.
Phototherapy will be stopped when the bilirubin level falls to a safe level, which usually takes a day or two.
Phototherapy is generally very effective for newborn jaundice and has few side effects, although your baby may develop a temporary rash and diarrhoea.