Smelly Gas: Do Charcoal Underwear, Pads or Pills Work?

Passing gas is normal. The worry for most people is the smell, especially on a plane, in a meeting or on a date. Here is what the lab tests found.

What makes gas smell

Researchers collected gas from 16 healthy volunteers fed beans to boost output.¹ The worse the smell, the more hydrogen sulfide (the rotten-egg gas) it contained.¹ Sulfur gases are the main, though not the only, cause of the odor.¹

That’s why a lot of gas can be fairly mild, and a little can be strong: the smell comes from trace sulfur, not the volume.

Charcoal products, tested

Activated charcoal traps sulfur gases well in the lab.¹ A later study tested charcoal products by having 6 volunteers wear sealed pantaloons over their clothes while a measured puff of smelly test gas was released:²

Product	Smelly gas caught
Ordinary clothes	About 22%2
Most seat cushions	About 20%2
Pads worn inside underwear	55% to 77%2
Briefs made of activated carbon fabric	Virtually all2

The products were those on sale in the mid-2000s, the test used a simulated puff, and instruments, not noses, did the measuring. Still, it’s a fair side-by-side comparison. UK guidance lists odor-absorbing underwear and pads among the options a pharmacist may suggest.³

Charcoal pills

Swallowed charcoal didn’t work in a small test. Five volunteers took activated charcoal four times a day for a week, with no drop in sulfur gases, total gas or symptoms.⁴ The charcoal’s binding sites likely fill up on the way through the gut.⁴

Other things that help

1. Eat smaller meals, slowly, and exercise regularly.³
2. Notice your triggers. Cabbage and onions are common ones.³ A food diary helps.
3. Ask a pharmacist about simethicone or odor-absorbing products.³

When to see a doctor

See a GP if gas is affecting your life and self-help hasn’t worked, or it comes with ongoing belly pain or bloating, constipation or diarrhea, or weight loss you can’t explain.³ See how much gas is normal and why you have so much gas.

Try: “I’ve had much smellier gas for the past two months, along with looser stools. Is this worth testing for, or could it be my diet?”

Bloated by Dinner covers this in Chapter 5, “Ten to Twenty a Day,” in a section called “The Pantaloon Studies.” Its Belly Clock logs meals beside gas and smell, so a pattern like a heavy-meat dinner and a rough evening shows up on paper. See the book.