It's important that your mum tells her doctor about this right away.
Chicken pox is an infection caused by the virus varicella zoster. The same virus also causes shingles. Both chicken pox and shingles can be unpleasant conditions but they are not usually serious. However in people whose immune system is not working properly (people who are immuno-compromised) these infections may lead to severe complications.
People who may be immuno-compromised include those who have had:
- chemotherapy within the past 6 months
- radiotherapy to large areas of their body in the previous 6 months
- a bone marrow transplant and whose immune system has not yet recovered
If someone has had chickenpox or shingles in the past they will have developed antibodies to the virus, and should be protected against further infections. But in people who are immuno-compromised this protection may not work as well.
Contact with chickenpox or shingles means being in the same room as someone with the infection for more than 15 minutes, or any face to face contact with them, such as talking to them.
Both chickenpox and shingles cause skin rashes. Chickenpox is infectious from 2 - 4 days before the rash appears until all the spots have crusted over, usually about 5 - 6 days later.
As your mum has recently had a treatment that might have reduced her immunity and has had contact with someone with chickenpox she should see her doctor immediately to get their advice.
Depending on her medical condition, and how her immune system is affected, her doctors may recommend one or more of the following things:
- a blood test to check whether or not she has antibodies to the virus
- treatment with an antiviral drug called acyclovir
- a course of varicella-zoster immunoglobulin which contains antibodies to the virus
If your mum needs treatment she may need to go into hospital for a few days for this.