When midges or gnats relentlessy lock on to their prey (a human), is it a sign of an underlying health condition or the nature of the gnat?

I’ve heard people tell me that they are constantly targeted by biting gnats/midges and horseflies (and such insects that draw blood) outdoors and in their homes or apartment buildings/ in their surroundings. Does this say more about the person’s underlying health or is it the nature of these insects to mercilessly hunt down their prey(to lock on to people and relentlessly follow them? I have never experienced such things and was intrigued by the accounts I’ve heard. I’ve heard everything from blood type to diet and a propensity to sweat profusely that contributes to such adverse experiences.

Here’s an article on reasons mosquitos are more attracted to some people than others. They’re referring to “experts” who may or may not be relying on good science, but what they mention echoes stuff I’ve at least seen marginal science for.

Now they’re talking specifically about mosquitoes, and the science I’ve come across so far has generally been on mosquitoes, but it’s at least plausible that it is similar for gnats/midges and horseflies. What is not mentioned in this article, and I’ve never seen elsewhere, even from spouters of pseudoscience like “it’s your bloodtype!”, is that biting insects care about health.