When we plan an aromatherapy treatment, we usually think carefully about our client. Which oils suit their needs? What dilution is appropriate? Are there any contraindications?
But there is another person exposed to those oils: the aromatherapist.
If you provide several treatments in a day, your hands may come into contact with several different blends. Add blending, teaching, a room diffuser and your own aromatherapy products, and it becomes a question worth asking.
Is there a maximum number of oils per day?
In the research and safety guidance reviewed for this article, I did not find a scientifically established maximum number of different essential oils that an aromatherapist should use in one day.
That does not mean unlimited use is safe. It means that counting bottles alone cannot tell us whether exposure is appropriate.
The oil selected, its concentration, the amount of product used, the frequency and duration of contact, and the condition of the therapist’s skin all matter. Inhalation and skin exposure also need to be considered separately.[1,2]
A daily limit expressed simply as “three oils” or “six oils” leaves out much of this information.
Three oils in a blend is different from three oils in a day
Keeping a blend simple can help you explain why each oil is included and assess its suitability. Two or three carefully selected oils may be sufficient for your treatment aim.
However, that is a practical blending approach, not a proven daily safety threshold.
There is also an important difference between the number of oils and the total dilution. If you prepare a blend at 1%, that means 1% essential oil in total, shared between the oils you have selected. It does not mean adding each of three oils at 1%, which would produce a 3% blend.
An individual oil may also have a safety limit below the overall dilution you planned. The blend must respect both its total concentration and any lower limit for a particular ingredient.[1]
Why the therapist’s exposure deserves attention
Your client may receive one treatment. Your hands may be in contact with massage products repeatedly throughout the working day.
Research supports taking this occupational exposure seriously.
A 2004 survey of 350 massage therapists found an association between using aromatherapy products and hand dermatitis. As an observational survey, it could not establish that those products caused every case.
A later study examined 128 massage therapists who already had occupational dermatitis. Sensitisation to fragrances or essential oils was identified in 42.2% of that group.[4]
That figure does not mean 42.2% of all massage therapists have an essential oil allergy. These were people being investigated for an existing occupational skin problem.
Neither study establishes a safe number of oils, treatments or drops per day. They do show why looking after the therapist’s skin belongs within professional aromatherapy practice.
What is sensitisation?
Sensitisation is the process through which the immune system becomes primed to react to a substance. Once an allergy develops, later contact can trigger allergic contact dermatitis.
An oil you have used comfortably for years may therefore become a problem. Previous tolerance does not guarantee future tolerance.[2]
Different essential oils can also contain some of the same fragrance constituents. Changing the oil’s name on the bottle does not necessarily remove exposure to the substance causing an allergy.
A case series involving massage therapists identified occupational allergy to oxidised fragrance constituents, highlighting another reason to pay attention to the condition and storage of oils.[5]
Simply rotating oils should not be treated as a reliable way to prevent sensitisation.
What can an aromatherapist do during a busy day?
These are practical ways to manage exposure, rather than a formula guaranteeing safety:
- Choose oils for a clear purpose and use an appropriate total dilution.
- Check the individual oil’s safety information and restrictions.
- Avoid getting undiluted essential oils on your hands while blending; use suitable dispensing equipment.
- Keep bottles tightly closed and follow supplier storage and shelf-life guidance.
- Consider plain carrier products when essential oils are unnecessary or unsuitable.
- Maintain client hygiene while using gentle hand cleansing, drying thoroughly and applying a suitable fragrance-free moisturiser.
- Check your hands for dryness, itching, redness or cracking.
The Health and Safety Executive advises reducing avoidable skin contact, protecting the skin and checking regularly for early signs of dermatitis. Persistent or recurring symptoms warrant advice from a GP or occupational health professional.[6]
If a product causes a reaction, stop using it and seek appropriate advice rather than continuing to test it on yourself.
What about a diffuser in the treatment room?
Room diffusion is another source of exposure for both you and your clients.
The Tisserand Institute recommends intermittent diffusion, typically 30–60 minutes on followed by 30–60 minutes off, with fresh air exchange. This is general guidance, not a guarantee that a particular oil or room concentration will suit everyone.[1]
For a therapist already working with aromatic products, it is sensible to consider whether a diffuser adds anything useful. A treatment room does not need a strong fragrance throughout the day.
My approach as an aromatherapy educator
I would encourage therapists to ask: “How can I make each use appropriate, while reducing unnecessary exposure?”
A thoughtful blend does not need a long ingredient list. Equally, a short ingredient list does not automatically make a product safe.
Consider your working day as a whole: the products touching your hands, the oils you handle while blending, the air in your room and the products you use at home.
Caring for your own skin deserves the same attention as caring for your clients.
At Karen Ashton School of Aromatherapy, my aim is to help you understand your oils, make informed choices and keep developing your knowledge as your practice grows.
Love Karen xx
Sources and further reading
- Tisserand Institute. Safety Guidelines. https://tisserandinstitute.org/safety-guidelines/
- Tisserand Institute. Irritation and allergic reactions. https://tisserandinstitute.org/safety/irritation-allergic-reactions/
- Use of aromatherapy products and increased risk of hand dermatitis in massage therapists (2004). https://pubmed.ncbi.nlm.nih.gov/15313817/
- Brans et al. Contact sensitizations in massage therapists with occupational contact dermatitis: Patch test data of the Information Network of Departments of Dermatology, 2008–2020. https://onlinelibrary.wiley.com/doi/full/10.1111/cod.14218
- Hagvall et al. Contact allergy to oxidized terpenes and occupational contact dermatitis in massage therapists – A case series (2020). https://onlinelibrary.wiley.com/doi/full/10.1111/cod.13494
- Health and Safety Executive. Skin at work: Prevention. https://www.hse.gov.uk/skin/employ/prevention.htm
Research reviewed: 8 October 2026.
Comments ()