Contrast therapy, the latest trend in wellness, is drawing in big numbers. Josie Adams goes to Auckland spa Hana to feel the burn (and the freeze).

I learned about onsen eggs last week. They’re eggs cooked very slowly at a low temperature – around 65°C. That’s slightly colder than an infrared sauna, one of which I stepped into only 12 hours after learning about the eggs.

In 1893 Dr Kellogg (yes, that one) invented the “electric light bath”, a tanning bed and sauna all in one. It took Europe by storm, and one sank with the Titanic. Now, 127 years later, the light bath’s child – the infrared sauna – may well be stacked on the Ever Given, ready for delivery to spas around the world.

Sara Higgins founded Auckland’s Hana spa to help bring four of these saunas to the New Zealand masses. They’re popular overseas and gaining traction here: no steam, what a dream! They use infrared light to cook us instead of wet hot air.

“People have likened the sauna to a microwave,” said Higgins. Eggs explode in microwaves. 

Hana is a spa centre built in an old Grey Lynn demolition and salvage yard. It’s a new beginning for the site and for Higgins, who used to be a pharmacist. The contrast therapy room has been open for only two weeks, but has already proved to be wildly popular.

You sit in the infrared sauna for 15-20 minutes and then get in an ice bath for as long as you can bear. Rinse and repeat. The therapy promises to help with inflammation, your immune system, post-workout recovery, detoxification – the list of alleged benefits is long.

“The general idea is that because the infrared is penetrating your body deeper rather than heating the air, it supposedly generates a deeper level of detox,” says Higgins.

Hana’s contrast therapy didn’t promise to coddle me. It promised to be gross and painful. It promised honour and machismo. I was keen. The sauna box was cedarwood and glass, and the lights glowed red. Higgins set the room timer to an hour and left me to undress and enjoy the technological advances in getting very hot and very cold.

The temperature gauge inside the sauna read 67°C.

An egg has a weight of 50g and takes 45 minutes to medium-soft boil at 65°C.

If I have a weight of 72,000g, or 1,440 eggs, it would take me 1,080 hours to medium-soft boil at the same temperature.

A normal (warm) bath is 45°C. This was a whole summer’s day hotter than that, and extremely dry. The air going into my lungs was hotter than the air coming out. I felt like I was on the verge of evolution. “I am the kwisatz haderach,” I muttered, and a fresh wave of sweat fell from my top lip.

It didn’t feel like I was producing sweat – the sweat was just appearing on me, like I was the victim of a disgusting magician. An iPad connected to speakers let me choose music or podcasts to listen to, but I had detoxed all music out of my brain and could only think to play the theme from Gremlins. I left Higgins’ meditation playlist going.

Time passed faster than I thought it would, and soon it was time for the ice bath. “We recommend anywhere from 10 seconds to three or four minutes,” Higgins had told me. She had laughed after saying “10 seconds”. I had laughed with her. It wasn’t funny.

When you put a hot egg in an ice bath, the shell cracks. So did I. I had my little rinse to get the sweat off, did my little run up the wooden stairs, and stepped into the bath. I screeched, stepped out, and backed away. “Fear is the mind-killer,” I told myself. “It is the little death that brings total obliteration.” I needed to make 10 seconds.

I went full Exorcist and planted all four limbs in the corners of the bath while I dipped my back in and out. Horrible. I knelt next to the bath and plunged my arms in for 10 seconds at a time. Harrowing.

Ice baths are for athletes. I am not an athlete. In high school my chosen sports were sailing and fencing, as if “swashbuckler” were a viable career choice. You don’t tear a lot of muscles in those sports. Mad Chapman, one-time Rock impersonator and The Spinoff’s closest thing to an athlete, has torn plenty of muscle fibres.

She was not impressed with my 10 seconds. “You realise that’s how long it takes your body to get used to it, right? You experienced the worst 10 seconds.”

The last time she took regular ice baths was as a teenager. “The actual science behind it was never fully explained to me at 15, but on day three of basketball nationals, it felt essential. 

“We would pick up a bunch of ice from the petrol station on the way back to the motel and run between an icy bath in someone’s room and the communal spa outside. It was mostly for our legs and made them feel like they didn’t really belong on your body but it definitely lessened the morning-after aches before our next games. 

“I don’t think I consistently move my legs enough any more to warrant having an ice bath ever again.”

I would also like to never have an ice bath ever again, but it did feel good for me. After an hour of moving between the inside of the sauna and the outside of the ice bath, I was energetic. My skin glowed, I felt extremely clean, and I was thinking very seriously about buying an LED face mask. The red light in the sauna was exciting.

But how good for me was it, really? Was my face just glowing because it was wet with sweat?

Dr Joy Hussain, a GP and PhD scholar at RMIT in Australia, said getting sweaty is, indeed, good for you. Her field of expertise is thermotherapy – basically, saunas. I wrote to her after my experience to confirm I had improved my health.

Hussain tried to research the difference between infrared saunas, traditional saunas and exercise last year, but the traditional sauna she was using sprang a water leak before the study could be completed.

“It’s too bad about the leak because we did find some interesting differences between infrared sauna and exercise when testing all the women,” she said. “Core body temperatures were higher with the infrared sauna, and breathing rates were much higher with the exercise.  Everything else was pretty similar.”

This means that in some ways, a cheeky 40-minute session in Hana’s infrared sauna could replace a gym session. Not in the ways of burning calories or breathing heavily, but it gets your heart rate up.

Is all the sweating and heart-thumping what detoxes us? And also, is “detoxing” even real? Hussain says it comes down to semantics. “When the medical establishment refers to ‘detox’ or detoxification, we’re usually talking about the assisted process of a patient ceasing the use of addictive substances,” she said.

“In alternative, complementary and naturopathic forms of medicine, ‘detox’ is more broadly defined as short-term interventions like diets, supplements, purification rituals et cetera designed to eliminate ‘toxins’ from the body to promote general health.”

Higgins plays it safe when clients ask her about the power of infrared. “There are a lot of people who say, ‘I’ve got this health condition, can it help?’ and at that point it’s important to say ‘it might’, or ‘it probably won’t’. I’m from a science background, I’m a pharmacist. I won’t say ‘yeah, sure, it’ll help’ unless I know that there is science behind it.”

“To be honest, not that many people ask.”

I am asking: can I bring an egg with me next time?

Contrast therapy at Hana costs $90 for 60 minutes. This was a gifted session.