Hot tubs, saunas & a compromised lymphatic system: the good, the bad and the ugly.
Why this matters:
If your lymphatic system is compromised (after cancer treatment, surgery, infection or primary lymphoedema), heat can be a friend or a foe. A client of mine noticed swelling after using after using a hot tub– a perfect real-life expample to unpack what’s going on and how to stay safe.
First, a quick science refresher 
(in normal words 
)
– Your lymphatics are a drainage-and-defence network. Tiny vessels collect fluid and proteins from tissues and return them to the blood stream.
– Collecting vessels are built from “segments” called lymphangions– each bounded by one-way valves. The wall has smooth muscle that contracts rhythmically (like a little heartbeat)– to propel lymph forwards. Scientists call the “beat quality” lymphangiomotoricity (you might see it also as lymphangion contractility/lymphatic pump activity). Temperature, stretch, and shear forces from flowing lymoh all modulate this pump. Moderate warming can increase contraction frequency up to a point, but extremes (too hot or too cold) can dysregulate flow.
(for a deeper dive, google – Lymphatic vessels and their surroundings: How local physical factors affect lymph flow)
The good (when heat might help)
– Water’s hydrostatic pressure can assist fluid return. Being immersed (especially deeper water) gently compresses the limbs and can aid venous/lymph return– one reason water based exercise is often helpful for oedema when water is thermoneutral (the range of ambient temperatures where the body can maintain its core temperature. Heat Production and Heat Loss are in Equilibrium/Balanced), to mildly warm, not hot.
(for more information on water-based exercise for upper and lower limb lymphoedema visit – https://doi.org/10.1016/just.jvsv.2022.08.002)
– Relaxation and pain relief– Gentle warmth reduces muscle guarding and can make movement easier– movement itself is a lymphatic booster. (See below for the BAD)
Takeaway – Pool exercise in temperate water can be great; it combines movement, hydrostatic pressure without the vasodilatory hit of very hot water.
The bad (how heat makes swelling worse)
– Vasodilation = more fluid leaking out! Hot environments (hot tubs, saunas, very hot baths, steam rooms, sunbeds) dilate skin blood vessels. That raises capillary filtration, increasing the load your already– compromised lymphatics must clear– so swelling can rise. UK guidance consistently cautions against high heat for people with or at risk of lymphoedema.
– Time and temperature matter. Risk climbs with hotter temps and longer exposure.
– Jets can be too aggressive. Strong spa jets directed at a swollen area can irritate the tissues and may worsen the congestion.
The ugly (infection risk and red flags)
– Skin infection rises in hot tubs.
– Cancer charities advise caution
So… can you ever use a hot tub or sauna?
Short answer: be cautious, and many people with lymphoedema decide they are not worth it. If you do choose to try:
A sensible, safety-first plan
1) Skip it if: you have any open skin, signs of infection, a current cellulitis/erysipelas history, or your swelling is already up that day.
2) Choose cooler and shorter: Keep water low (under 39*) and limit your time (10-15 suggested). I would suggest no more than 3-5 mins on your first try, and make sure you time it. It is very easy to lose track of time when chatting or feeling relaxed with the warmth. Stay away from the jets, as they may be too strong.
3) Compression timing: Remove compression garments in hot water, reply once you are cool and dry. Elevate the limb for 20-30 mins afterwards
4) Hydrate & cool down: Rinse & Cool the limb with a tepid shower, moisturise to protect and then pop your compression garment back on. (If you are joining your friends for a spa day, avoid alcohol around the session as it is a vasodilator)
5) Monitor “your dose response”– measure and visually compare before and after. A tight watch strap, a limb feeling a bit heavy, your rings feeling a bit tighter, these are signs of swelling. If you notice even a mild response in the hours and even the next day, it would be safer to avoid in future.
You can find lots of information
Lymphoedema Support Network – Cancer Research UK
Better alternatives for many people
– Thermoneutral pool exercise (waist-to-chest depth) for 20-30 minutes: You are moving, you have hydrostatic pressure, but you are not adding the heat
– Gentle self-care: Diaphragmatic breathing, a short walk, elevating the limb, some self MLD (your therapist will guide you), then compression
And… A bit more science. Lymphangions & lymphangiomotoricity– a quick 1 paragraph dive
A lymphangion is a short segment of a collecting vessel bounded by valves (these form a line with nodes interspersed, like a beaded necklace). It’s smooth muscle generates automatic, rhythmic contractions that pump lymph– this pump quality (frequency + strength) is your lymphangiomotoricity (a clinical term you will also see as contractility/pumping). It’s tuned by temperature, stretch and shear– mild warming, can speed the “beat”, but excessive heat or cold and certain mechanical loads, like too much pressure and even pain can disrupt this, so flow becomes inefficient.
So… What do official guidelines say?
– Macmillan – “Be careful using saunas, hot tubs and steam rooms… Only spend short amounts of time… Check swelling does not get worse.”
– NHS (England & Scotland) – Avoid very hot baths/showers; heat from saunas/steam rooms/sunbeds may increase swelling.
If swelling does flare up after heat
Back to basics: rest, elevate, breathe, gentle movement, and consistent compression until baseline returns.
Watch for infection: heat, redness, tenderness, flu-like symptoms– seek medical attention promptly; cellulitis guidelines for people with lymphoedema stress early antibiotics.
Thoughts…
– Hot tubs/saunas = common swelling triggers when lymphatics are compromised.
– If you experiment, keep it cooler, shorter, and never with broken skin– STOP if your swelling worsens and seek advice.
– For most, thermoneutral pool exercise beats hot water soaks.
You can find a simple guide to your lymphatic system here https://pilatestherapyandbodywork.com/the-lymphatic-system-and-you/
Please get in touch if you would like to book an appointment for a consultation fi@therapyinmotion.co