Blue urine, blue skin and dye reactions after sentinel node biopsy

Yes. If blue dye was used to find your sentinel lymph node, some blue colour afterwards is expected and usually harmless. The dye is injected into the breast during surgery so the surgeon can see the lymph channels and nodes. Some of it is absorbed into the blood and leaves the body through the kidneys, so your urine may look blue, green or turquoise for a day or two. Your stools can also look greenish. The skin around the injection site, and sometimes a wider area of the breast, can look blue or grey. This staining often fades within weeks, but in some people a faint patch lasts many months, and occasionally longer, especially after breast-conserving surgery where the breast tissue stays. Right after surgery your skin, lips or face may look slightly bluish, and the finger clip that measures oxygen may give a falsely low reading for a short time. These effects are not a sign of harm. Less commonly, the dye causes an allergic reaction, ranging from a raised itchy rash or hives to, rarely, a sudden drop in blood pressure that the anaesthetic team treats straight away. Reactions nearly always happen during the operation, when you are closely watched. If you notice a rash, swelling or breathlessness at home, seek urgent medical help.

Blue urine is expected

It usually clears within one to two days.

Skin staining fades slowly

Most fades over weeks to months, though a faint mark can linger.

Allergy is uncommon

Serious reactions are rare and are usually caught in theatre.

Dye effects are usually minor, but it is fair to be clear about the uncertain parts.

Staining time varies widely

Some people see the colour gone in a few weeks; others keep a faint mark for a year or more. Nobody can predict exactly how long yours will last.

Reactions cannot always be predicted

People with no known allergy can still react. That is why the anaesthetic team watches closely after the injection.

Staining can affect later checks

A lingering blue patch is harmless, but tell anyone examining your breast later that dye was used.

What this page cannot tell you

It cannot say which dye your hospital uses or whether a mark on your skin is dye. Your team can check.

A short conversation before your operation helps the team choose the safest way to find your sentinel node.

Past reactions

Mention any reaction to dyes, contrast used for scans, hair dye, cosmetics or medicines, even if it seemed minor.

Other allergies and asthma

People with several allergies may be at slightly higher risk. Your team may then prefer a radioactive tracer or another marker.

Pregnancy

Blue dye is usually avoided in pregnancy. A tracer alone is generally used instead.