A small red bump or a little pus can appear where your baby had the BCG vaccine. You may notice it while bathing or changing your baby, then wonder whether the site can get wet or needs a dressing. [2][4]
Why can redness or a small sore appear weeks after BCG?
Some babies develop a small red bump or ulcer at the injection site about two to four weeks after BCG vaccination. It may then take a few more weeks to heal gradually. A small scar may remain, while some babies have no obvious scar. [4]
A little pus can be part of this local reaction. If the site is getting worse or is not settling, though, ask a healthcare professional to check it rather than assuming it is an expected reaction. [2][4]
An enlarged gland can also cause a lump under the armpit in some babies. If you notice a change that concerns you, contact your healthcare team for advice. [4]
Can your baby bathe, and how should you care for the site?
Scroll sideways to compare all details.
| Your question | What to do |
|---|---|
| Can my baby have a bath?[1] | Your baby can usually bathe as normal. Keep the injection site clean and dry. |
| What if the site needs cleaning?[1] | Family Health Service advice is to use cooled boiled water if needed, then dry the site with clean gauze. |
| What should my baby wear?[1] | Choose loose clothing so it does not press against the site. |
| Should I apply cream or a plaster?[1] | Do not apply medicated powders, solutions or ointments yourself, or cover the site with a plaster, dressing or bandage. |
If a clinician has checked your baby and given specific care instructions, ask them to explain anything you are unsure about.
When should you have the BCG site checked?
Take your baby to a Maternal and Child Health Centre if the reaction gets worse or does not settle. You can also contact or visit a Chest Clinic if you have concerns about the reaction. You do not need to know whether the site is infected before asking for help. [2][4]
When you call or visit, tell the healthcare professional:
- When your baby had BCG and when you first noticed the change.
- Whether the site is improving, staying the same or getting worse.
- Whether you have put any medicine or other product on the site.
Get urgent help for breathing difficulty or collapse
If your baby has trouble breathing or collapses, seek emergency medical help immediately. These signs need urgent care and should not be treated as an ordinary injection-site reaction. [5]
Related reading
Preparing a baby for vaccination and general aftercare
What is covered under the Hong Kong Childhood Immunisation Programme?