Diarrhoea and rash on pertuzumab

HER2 and its partner proteins are not found only on cancer cells. Related proteins also help keep the lining of the bowel and the skin healthy, so blocking them can upset these tissues. That is why loose motions and skin changes are the two side effects most linked to pertuzumab. Diarrhoea is very common when pertuzumab and trastuzumab are given with chemotherapy, and it often starts in the first few days of a cycle. Most episodes are mild or moderate, and they usually become less troublesome once chemotherapy stops, although some people have milder loose motions for as long as they have the antibodies. The key is acting early: drinking plenty of fluids, eating plain food and taking the anti-diarrhoea medicine your team recommended as soon as motions become loose. Severe diarrhoea, diarrhoea with fever, or signs of dehydration need urgent advice, because fluid loss can become dangerous quickly, especially if your white cell count is low. Skin effects include a spotty or acne-like rash, dryness, itching and changes around the nails. These are usually mild, and a good skin routine with gentle soap and regular moisturiser helps most people. Your team may suggest creams or tablets if a rash spreads or becomes sore. Both problems are rarely a reason to stop treatment when they are managed well.

Act on the first loose motion

Early fluids and medicine prevent most diarrhoea from becoming severe.

Skin care prevents a lot

Moisturising every day and avoiding harsh soaps reduces rash and dryness.

Fever changes everything

Diarrhoea with a temperature needs same-day medical assessment.

Home measures help a great deal, but they have limits, and it is important to know when to stop managing things yourself.

Not every diarrhoea is the medicine

Infections, other medicines or food can also cause loose motions. Your team may test a stool sample if symptoms are severe or unusual.

Delays sometimes happen

If diarrhoea is severe, a cycle may be postponed or chemotherapy adjusted. This protects you and does not usually reduce the value of treatment.

Skin effects can be persistent

Dry skin and nail changes may continue while you are on the antibodies, even with good care.

What this page cannot tell you

It cannot judge your own symptoms. If you are unsure whether something is serious, contact your treatment unit rather than waiting.

Nail changes can develop slowly over weeks and are easy to overlook until they become sore.

Everyday care

Keep nails short and clean, avoid biting them or pushing back cuticles, and wear gloves for washing up, cleaning and gardening.

Footwear

Choose comfortable, roomy shoes and cotton socks to reduce pressure on toenails.

Signs of infection

Redness, swelling, pus or throbbing pain around a nail may need antiseptic soaks or antibiotics, so show it to your team.