What you can and cannot put on your skin during radiation

There is one instruction that covers most of what follows. NCI's radiation guide says to check with your doctor before using any skin products on the area being treated.

Not most products. Any.

That sounds excessive until you understand why. Skin inside a radiation field is being asked to withstand repeated doses over weeks. Anything that irritates it, dries it, coats it or reacts with it is working against tissue that is already under strain.

NCI specifically warns against using the following on the treatment area without medical approval:

• Bubble bath
• Cornstarch
• Cream
• Deodorant
• Hair removers
• Makeup
• Oil
• Ointment
• Perfume
• Powder
• Soap
• Sunscreen

Some of those will surprise you. Cornstarch has a long folk reputation for soothing skin. Sunscreen is normally the responsible choice. Soap is not optional in most people's minds.

That is the point of the list. It is not a list of obviously harsh chemicals. It is a list of things most people would apply without a second thought.

Assume nothing is approved until your radiation team tells you otherwise.

This is the one people ask about most, particularly during breast radiation where the underarm may be in or near the field.

NCI includes deodorant among the products to clear first, and its guidance on radiation skin care tells you to ask your team which products, such as powder or antiperspirant, you should avoid before treatment.

Practices differ between centres, and your team knows exactly where your field lies. Ask them directly. If the answer is no, ask what you can do about odour, because that is a real quality-of-life issue and they will have heard the question before.

Two categories are not a matter of checking first.

NCI says not to use heating pads, ice packs or other hot or cold items on the treatment area. Skin in a radiation field has altered sensation and reduced ability to cope with temperature extremes, and it is easy to cause damage you cannot feel happening.

Bandages are also not to be used on the treatment area, according to NCI's skin guidance. If the skin has broken down and you think it needs covering, that is a reason to phone your team, not a reason to reach for a dressing from the bathroom cupboard.

NCI's positive guidance is short.

Take extra good care of your skin during radiation therapy. Be gentle, and do not rub, scrub or scratch. Use only lotions your doctor has approved, and wear soft fabrics.

The soft fabrics point deserves more attention than it gets. Seams, underwires, stiff collars and rough waistbands sit exactly where treated skin is most vulnerable, and rubbing all day is its own kind of damage. Loose cotton over a treatment area is worth reorganising a wardrobe for.

The most useful thing you can do at your planning appointment is come away with a concrete list.

Ask which moisturizer they want you using and when to apply it. Ask what to wash with. Ask about deodorant, sun protection and shaving. Write the answers down, because you will not be able to reconstruct them in a shop three weeks later.

The restrictions do not lift the moment your last session ends. Skin keeps reacting for a while after treatment stops.

Ask your team when you can return to your usual products. Ask separately about sun protection for the treated area in the longer term, because that question has a different answer and a longer timeframe.

• Call your care team the same day if treated skin turns into sores that are painful, wet or look infected. NCI calls that a moist reaction.
• Call your care team within a day or two if a product you used has left the treated area stinging, swollen or much redder, or if dryness and itching are getting worse despite the lotion you were given.