Everything on this site is general education, not medical advice. Deliberate cold and heat are real physiological stressors, that's why they work, and why they deserve respect. Talk to your GP before starting if you have any medical condition, take medication, or are unsure.
The detailed guides
This page covers the rules that apply to everything. Each therapy then has its own guide with session limits, warning signs and product-specific checks:
Who should talk to a doctor first
Cold water immersion
- Any cardiovascular condition, arrhythmia, or history of heart attack or stroke
- Uncontrolled high blood pressure, cold sharply and briefly raises blood pressure
- Raynaud's phenomenon, cold urticaria or cryoglobulinaemia
- Pregnancy
- Epilepsy or seizure history
Sauna & heat
- Cardiovascular conditions or very low blood pressure
- Pregnancy
- Conditions or medications that impair sweating or temperature regulation
- Multiple sclerosis or any condition where heat worsens symptoms
- Active infection or fever, wait until it passes
Many people with managed conditions use cold and heat safely under medical supervision. The point isn't to scare you off, it's that your doctor should be in the loop before the first session, not after an incident.
Hard rules
- Age. Our products are sold to adults (18+). Users aged 16–17 should only use them with an adult present; they're not intended for children under 16.
- Never use cold immersion alone, have someone within earshot, especially when new.
- Never mix alcohol or sedatives with cold or heat. Alcohol impairs temperature regulation and judgement in both directions, it's the single most common factor in sauna and cold-water incidents.
- Exit immediately on dizziness, chest tightness, numbness or confusion.
- Never use a sauna while drowsy, and never sleep in one.
- Follow the printed manual for electrical setup. Water and electricity demand respect: plug units directly into a suitable socket, keep controllers dry, and use a licensed electrician where the manual requires a dedicated circuit (the Hemlock stove does).
Sensible session guidance
Start conservative. Cold: 2–5 minutes at 10–15°C is where most of the research sits, colder isn't automatically better. Heat: 15–20 minutes at 70–90°C with cool-down breaks, hydrating between rounds. Build up over weeks. More detail, with citations, on the science page.
No protocol is worth pushing through warning signs, the adaptation comes from consistency, not heroics.