My 18-year-old son Jonah is skinny. Really skinny. Every-rib-poking-through-the-skin skinny. So when he stomped out of his bedroom on a humid, late August morning wearing two long-sleeved T-shirts and fuzzy pajama bottoms because he said his room was an ice box, I shrugged.

Of course he’s cold. He’s got no body fat, I thought.

His complaints about being freezing, about having to layer on a comforter and an extra blanket when he slept, were quickly echoed by his twin sister and younger brother, both of whom were dressed for a winter night’s slumber.

The coolness of our home’s overworked air conditioner doesn’t chill me as it does them. Putting aside recent peri-menopausal hot flashes that have seriously messed with my internal temperature gauge, I need the air to be on the cooler side. Lower temperatures keep me lucid, prevent me from getting lightheaded, from seeing spots, from nausea that makes me curl into a lowercase “c”, from my knees buckling. But seeing my heavily layered teens on a bright summer morning, I had to admit that my highly air-conditioned life was starting to become a problem, albeit a problem with no real solution.

I like to blame all of this on a 19th century German doctor. A guy named Uhthoff. Wilhelm Uhthoff. He discovered that patients with Multiple Sclerosis experience a temporary flare-up of symptoms of their disease when they become overheated. These days, when an MS patient becomes too hot and, as a result, some of her symptoms resurface—like blurry vision, mobility and balance issues, nausea—it’s called Uhthoff’s Syndrome (or Uhthoff’s Phenomenon or, occasionally, Uhthoff’s Sign).

I was diagnosed with Relapsing-Remitting Multiple Sclerosis—the autoimmune disease where my nervous system attacks the protective myelin that covers nerve endings—in August 2014 at age 45, after a difficult two-year-long diagnostic process. I now take twice-daily pills intended to reduce MS attacks and slow down the progression of the disease. For all the good I’m hoping this medicine is doing to help me live my life as close to “normal” as I can, it cannot protect me from the effects of heat and the humidity.

Long before the advent of MRIs—which allow neurologists to identify lesions left behind by assaults on the brain and spine—doctors, inspired by Dr. Uhthoff, utilized what they called the “hot bath test” as an investigative tool. “A person suspected of having MS was immersed in a hot tub of water,” the National Multiple Sclerosis Society’s website says. “The appearance of neurological symptoms or their worsening was taken as evidence the person has MS.” Walking around outside in heat and humidity, spending time in an overheated room, and getting too hot overall can temporarily cause an MS patient to experience what feels like an MS exacerbation but the symptoms fade when the person cools off. Even “a very slight elevation in core body temperature” can “impair the ability of a demyelinated nerve to conduct electrical impulses,” the MS Society says.

My life is now dictated by the temperature. Meteorologists are my soothsayers. Their forecasts tell me if I can attend the upcoming Boston Red Sox game or whether the heat and humidity will make me wilt like a sunflower without water well before the seventh inning stretch. They tell me if I need to tuck ice packs into my purse which I can press to my face, neck and arms so I can watch my elder son participate in Jazz Night in the steamy high school gym in early June without becoming ill. They inform my decision as to whether I can witness my daughter reach her personal best in the high jump during a track meet or whether the heat and humidity will be too intense for me. If I’m uncertain about whether the conditions may cause me difficulties, I have to either find a way to cool off or skip events altogether.

What the meteorologists cannot do is prepare me for the unpredictable situations, like when I visited the Quincy Market food court in Boston with my family at the end of December 2015. I discovered the heat was cranked up. High. It was like stepping into the Caribbean. The customers’ heavy winter coats emitted a damp, choking stuffiness into the air. All of this caused an adverse reaction inside my damaged brain, one that buckled my knees and made me see spots. I told my husband and three teens that I’d wait for them outside on the steps, where I stood, for a full 15 minutes, in a thin shirt and jeans in 30-degree weather in order to regain my bearings, my wool coat, sweater, scarf, gloves and hat on the ground at my feet, like snakeskin that had been shed.

Teaching at a local university is also a crapshoot about which the meteorologists are likewise of no help. Inside a classroom that has no windows and no thermostat, I had to start dressing in thin layers, with sleeveless dresses and blouses at the base. I was never sure if the room would be cool or whether the heat would be blasting, so my wardrobe, more often than not, looked like I was perennially ready for summer.

Throw in the nascent beginnings of one of the most quotidian symptoms of perimenopause for women of a certain age—unpredictable hot flashes—and I feel trapped inside a vessel with an out-of-whack temperature gauge. Sometimes I feel as though I’m at war with this fleshy mass and my only armor comes in the form of ice packs, vigorous air conditioning, and sleeveless blouses and dresses in all kinds of weather, no matter how ridiculous it looks.

So when my children emerge from their bedrooms wrapped in blankets on a moist late August morning while I’m comfortably sipping iced coffee while wearing shorts and a T-shirt, I have no good answers for them. If I don’t jack up the AC, I will be a listless puddle on the floor of use to no one. I guess I’ll have to buy them more blankets.

Meredith O'Brien teaches journalism at Northeastern University. The Boston- area author of the newly-released Mr. Clark's Big Band: A Year of Laughter, Tears and Jazz in a Middle School Band Room—about a jazz band's year of grief and recovery after the sudden death of a classmate—O'Brien is nearing completion of an MFA in creative nonfiction from Bay Path University. A former newspaper reporter, investigative journalist and weekly columnist, O'Brien is currently working on a memoir about life as a Multiple Sclerosis patient. Read more about her work at and follow her on Twitter, @MeredithOBrien.