When you fall ill, your own system will manufacture antibodies to counteract the particular illness you are having, whether it be influenza or chickenpox or measles for that matter. These antibodies will be passed on to your baby through your milk. All these illnesses are contagious, and it is likely that your baby has already been exposed to the germs. To interrupt the breastfeeding at this stage means that your baby has been exposed, but will be deprived of the protection of antibodies from your milk. she is more likely to come down with the illness. If breastfeeding is continued, her exposure is at least partially neutralised by the antibodies in your milk. She may not get it at all, or be hit very lightly with the illness.

In the case of chickenpox, babies older than 6 months may weather an exposure quite well, and even benefit from having it lightly under the protection of breastmilk. It may be advisable to protect very young babies (under 1 month) from exposure, as there may be more complications when very young babies are infected. If the very young baby can be cared for temporarily during the infectious period, and still receive expressed breastmilk, she will benefit both ways.