By Zolene, Massage Therapist · Updated 31 August 2026
Two tubes sit side by side on the same shelf. One is a licensed medicine with a drug in it. The other is a cosmetic that works on sensation alone. Nothing on the front of either box makes that obvious, and almost every argument people have about which muscle product is best is really this confusion in disguise.
- A licensed medicine carries a PL number on the box. A cosmetic does not
- Diclofenac and lidocaine products are medicines, with doses and warnings
- Menthol creams and gels are cosmetics, working through cold-sensing nerves in the skin
- A stronger sensation tells you nothing about which category you are holding
- Massage therapists should work with cosmetics only, and there is an insurance reason for that
- The ten second shelf test is the back of the box, not the front
In This Article
- Why do some muscle gels have a PL number and others do not?
- What is diclofenac gel, and how is it a different kind of product?
- Does a stronger sensation mean it is a medicine?
- What does cosmetic actually mean on a muscle cream label?
- Why will a massage therapist not put your own gel on you?
- How do you tell which is which in ten seconds?
- When should you talk to a pharmacist instead?
Why Do Some Muscle Gels Have a PL Number and Others Do Not?
Because they are legally different things. A PL number, short for Product Licence, is issued to a medicine that has been through regulatory assessment. If a product carries one, it is a licensed medicine. Cosmetics are regulated under separate law, are never issued a PL number, and do not carry one. It is the single clearest marker on any box.
You will usually find it in small print on the back or the side, often near the batch number and the expiry date, written as PL followed by a string of digits. It is not hidden, but nobody tells you to look for it.
The reason the two sit side by side is that they are sold to solve the same felt problem from opposite directions. One acts on the body. The other acts on what you notice. Both are legitimate. They are just not interchangeable, and the shelf does nothing to help you tell.
What Is Diclofenac Gel, and How Is It a Different Kind of Product?
Diclofenac is a non-steroidal anti-inflammatory drug, the same family as ibuprofen, delivered through the skin rather than swallowed. Products containing it are licensed medicines. They have an active ingredient at a stated strength, a maximum daily amount, an age limit, and a list of people who should not use them at all.
The NHS guidance on NSAIDs sets out who they suit and who they do not. Lidocaine products are a different case again: lidocaine numbs, which is a pharmacological action, and that also makes those products medicines.
None of this makes medicines better. It makes them a decision with consequences, which is why a pharmacist is standing there.
Does a Stronger Sensation Mean It Is a Medicine?
No, and this is the assumption that costs people the most money. Intensity of sensation and regulatory category are unrelated. A cosmetic menthol product can feel far more dramatic on the skin than a licensed medicine that you barely feel at all. The medicine is doing something you cannot always feel. The cosmetic is doing something you can feel.
I watch this play out constantly. Someone tries a very strong cooling product, feels it properly, and concludes it must be the powerful one. Then they try a medicated gel, feel almost nothing, and decide it is not working. They have it exactly backwards, and no packaging in the country corrects them.
People buy sensation and think they are buying strength. They are two completely different things, and only one of them is on the label.
Zolene, Massage Therapist and founder of Muscle Mint
What Does Cosmetic Actually Mean on a Muscle Cream Label?
It means the product is intended to work on the surface of the skin, and that it is not permitted to claim otherwise. A cosmetic changes how an area feels. Menthol binds to a cold-sensing receptor called TRPM8, so the nerve sends the same signal it would if you were holding something genuinely cold, while the skin stays exactly the same temperature.
The line is not decorative. The MHRA's Guidance Note 8, updated in May 2026, sets out how a product is judged, and it looks at the whole presentation: the name, the claims, the composition, the way it is sold. A product that reads as a medicine is treated as one, whatever the maker intended.
Which is why an honest cosmetic label sounds underwhelming. It has to.
| Licensed medicine | Cosmetic | |
|---|---|---|
| PL number on the box | Yes | No |
| Typical ingredients | Diclofenac, ibuprofen, lidocaine | Menthol, camphor, essential oils |
| How it works | A drug acting in the tissue | A sensation on the skin surface |
| Stated dose and limits | Yes, with warnings | No, but patch test first |
| Who to ask | Pharmacist or GP | Your own preference |
Why Will a Massage Therapist Not Put Your Own Gel on You?
Because supplying or applying pharmaceutical products sits outside what a massage therapist's insurance covers. Massage therapy is not statutorily regulated in the UK, but insurers set the boundary, and applying a licensed medicine to a client is a standard exclusion. That is why every product on every massage couch in the country is a cosmetic.
This comes up more than you would think. A client arrives, produces a tube from their gym bag, and asks me to use that instead. I say no, and then I explain why, and most people are surprised there is a rule at all. It is not fussiness. If something went wrong, I would be applying a medicine I am not covered to apply.
There is a duller reason too. The smell most people associate with a classic muscle rub, is stubborn. It transfers onto hands, onto linens, and it survives a hot wash. Use one of those on the first client of the day and the next five smell it too. Ask any therapist why they are particular about products and the honest answer is half about safety and half about laundry.
How Do You Tell Which Is Which in Ten Seconds?
Turn the box over and look for three things. A PL number means it is a licensed medicine. A named active ingredient with a percentage strength means the same. A dosing instruction, such as how many times a day and for how many weeks, is the third giveaway. If you find none of those and instead see a full ingredients list in Latin plant names, you are holding a cosmetic.
Full disclosure: one of the products in this category is mine, so read the next paragraph with that in mind.
Muscle Mint is a peppermint and eucalyptus menthol cream in a sunflower oil base, made in Northern Ireland, UK. It creates a strong, temporary cooling tingle on the skin. It is a cosmetic product, not a medicine, it carries no PL number, and it does not treat anything. If you want to know what to look for across the whole category rather than in one bottle, I have written that up separately in my guide to what actually makes a cooling rub good.
When Should You Talk to a Pharmacist Instead?
Any time the question is medical rather than sensory. If something followed a specific injury, if it is getting worse rather than better, if it has lasted more than a couple of weeks, or if it comes with numbness or fever, that is a conversation for a pharmacist, a GP or a physiotherapist. No product on the open shelf answers those.
Ask before combining things, too. People layer a medicated gel and a cooling cream on the same patch of skin without thinking about it, and that is worth a question rather than an assumption. The same goes if you are pregnant or breastfeeding, or already using other creams or patches on that area.
And whatever you end up with, patch test it on a small area first, and keep it away from broken or irritated skin, your face and your eyes. Our own directions and safety page covers that for anyone who wants the detail.
Related Reading
Frequently asked questions
Is Voltarol a medicine or a cosmetic?
Do cosmetic muscle creams have a PL number?
Is a cosmetic cream weaker than a medicated gel?
Can you use a menthol cream and a medicated gel on the same area?
Do massage therapists use medicated gels on clients?
Written by Zolene
Zolene is a massage therapist with more than fifteen years of hands-on experience. She created Muscle Mint in Northern Ireland, UK, for the minutes after effort.
Read the Muscle Mint story
