Kristen Thrush is a mom to seven kids.

But one of her children, 18-year-old Rachel, has never been “normal” when it comes to her body temperature. Rachel never seems to spike above 99, even when she is clearly fighting an infection and clearly not feeling well. Her typical body temperature usually rests around 97 degrees.

“We’ve had her take it two or three times sometimes.. you didn’t have it under your tongue the right way,” Thrush said.

But Rachel might not be all that different after all. The standard body temperature of 98.6 was set back in 1871 by a German doctor. More recent research by Stanford University, however, suggests that since then humans have cooled off a bit, settling instead around 97.5.

The study speculates that multiple factors, like better hygiene and medical care, could have contributed to the drop in temperature.

The issue is something Dr. Joan Thode of Penn Medicine Lancaster General Health Physicians Roseville Pediatrics hears often.

“It’s not uncommon for us to hear, ‘my kid is a 97 so a 99 is a fever for them,” Thode said.

But Thode warns that far more research needs to be done in order to change the medical definition of a fever which is 100.4 for infants and 100.8 for kids and adults.

She suggests, instead of focusing on a number, you should focus on how your child is feeling.

“If your child is looking sick and acting sick, they’re probably sick,” Thode said.

What’s more; Dr. Thode said you should keep your kids home accordingly. Just because their temperature doesn’t reach a fever threshold, doesn’t mean they aren’t contagious.

“If they’re below that threshold number wise, but they look kind of drawn and peaked, clearly not feeling well, then I still put them in a category that they should be home until they bounce back,” Thode said.

Thrush said it took years, but she finally accepted that a fever in her daughter is not the same as a fever in her other kids. And this study, she said, is validation.

“It made us think like, okay, we’re not crazy,” Thrush said.

To read more on the Stanford study, click here.