Science, technology, engineering and mathematics are popular topics on YouTube. Some channels that stream videos on these subjects have millions of subscribers. Most are hosted by men.

“There is a lot of discussion about YouTube being an unpleasant environment for female creators,” said Inoaka Amarasekara, an Australian researcher in science communication. “I wanted to see if that affected science communication on YouTube, and if that was something I could corroborate.”

In fact it was.

“She so ugly I almost threw up. Ew.”

“I was just staring at your bbbooo.....i mean eyes.”

“Go back to the kitchen and make me double stack sandwich.”

These are some of the 23,005 YouTube comments that form the basis of a new paper by Ms. Amarasekara and Will Grant, a lecturer at Australian National University, published last week in the journal Public Understanding of Science. They found a tough environment for women who create YouTube videos centered on science, drawing both more comments per view than men and also a higher proportion of critical comments as well as remarks about their appearances.

“The comment space for women on YouTube seems to be more volatile, both positive and negative,” Dr. Grant said.

Ms. Amarasekara didn’t feel confident that an automated sentiment analysis could capture the meaning of the comments, so she manually sorted each of the thousands of comments into one of six categories: positive; negative or critical; hostile; sexist or sexual; appearance-based; and neutral or general discussion. Of course, that meant she had to read them all.

“I was quite disappointed by the time I’d gone through them,” she said. “I could see why people would not want to be on YouTube.”

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The researchers found that about 14 percent of comments for female on-camera hosts were critical, compared to about six percent for male hosts.

They also found female hosts got a much larger proportion of comments about appearance (4.5 percent for women versus 1.4 percent for men) and comments that were sexist or sexual (nearly three percent of comments for women versus about a quarter-percent for men).

There were some positives for women as well. Female on-camera hosts elicited more comments, likes and subscribers per view than the other categories. They even received a slightly higher percentage of positive comments compared to male hosts.

Some of the researchers’ findings echoed a 2014 study that looked at comments on TED Talks. When the presenter was a women, 15.28 percent of comments were about her as opposed to the talk, TED or other topic. When the speaker was a man, only 9.84 percent of comments were about him.

That study also found that comments for videos with female presenters tended to be more “emotional” — significantly both more positive and negative.

Facing YouTube critics is like “someone is leaving a Post-it note on your desk every day telling you why you’re not qualified or why your voice is horrid,” said Vanessa Hill, who has 435,330 subscribers on her channel BrainCraft.

“I’m sure it does discourage some female creators from starting a channel, but I think it goes further than that,” she said. “It discourages female creators from continuing to make videos and being able to do that at a professional or semiprofessional level.”

Indeed, Ms. Amarasekara ran into an obstacle immediately with the study, which was started in 2015 as part of her master’s thesis, because of the lack of women-led channels.

After getting lists of the 370 most popular YouTube channels in science, technology, engineering and math, she realized only 32 were hosted by women — not enough for a significant sample size. To flesh out the study, she added 21 women-hosted channels from a list compiled by Emily Graslie, host of the popular science YouTube channel The Brain Scoop.

In the study, Ms. Amarasekara cited Ms. Graslie’s 2013 video, “Where My Ladies At?,” which posited that sexist, appearance-obsessed comments might be partly why there were so few female-led STEM channels.

Since then, Ms. Graslie says, her channel’s community has gotten more positive — but she’s frustrated that the conversation about women on YouTube doesn’t seem to have evolved.

“We’re still talking about women struggling to be successful on a platform, and yet I’m still only asked about something I made five years ago,” she said. “I wish I got more recognition for the other 200 videos that I’ve made.”

Recently, Ms. Graslie has posted videos about meteorites, a skunk dissection and a bird specimen that was donated to her employer, The Field Museum in Chicago, by a convicted murderer.

YouTube allows creators to block comments with specific words and phrases. Creators may block their own home address, for example, as well as share lists of words that tend to pop up in hostile comments. But Ms. Graslie also questioned whether YouTube could do more to support women on its platform.

“The comment section on YouTube just isn’t built for constructive conversation,” she said. “The most controversial comments seem to be the ones that rise to the top.”

When asked about the study, YouTube said in a statement, “We don’t tolerate hateful or abusive comments and remove them when flagged. Additionally we provide uploaders with tools to moderate, disable and even hold potentially objectionable comments for review.”

Ms. Amarasekara and Dr. Grant believe more research is needed around broader gender categories as well as factors like ethnicity, sexual orientation and physical ability, which could help improve how scientific information is communicated to the public.

“If you have diverse voices, you’ll reach more diverse audiences,” Ms. Amarasekara said. “If you want to reach more people, you need people who speak to them.”