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Moss Safety: Is it Poisonous or Non-Toxic?

Moss seems to grow everywhere, especially in the pacific northwest where I live. A natural question you might be having either out of sheer curiosity, genuine concern, or in preparation for taking on a strange dare is whether or not moss is poisonous.

Fortunately, there are no reported moss species that are poisonous or that can cause allergic reactions. On the contrary, moss has been used historically as a wound dressing due to its antiseptic properties. It’s also been used as an ailment for coughs, inflammation, and stomach aches.

In case you’re still skeptical, let me break down for you why moss is completely safe to handle and why it might be mistakenly thought to cause allergies.

Why Moss Is Not Poisonous

As far as I’ve been able to find, there are no poisonous mosses and there are no cases reported of moss poisoning. 

As one of the relatively simple plants, moss doesn’t have the structures or functions in its cells to produce toxins, unlike plants like poison ivy or poison oak which produce oils that cause allergic reactions.

However, I was able to find this article from the NY Times where researchers found contaminated moss due to pollution coming from a glass factory. More specifically, they found 346 samples of moss contaminated with cadmium, a toxic chemical that can cause cancer and kidney malfunction.

Moss is known to absorb heavy metals and contaminants, especially because it doesn’t have any cuticle (the waxy layer that makes leaves hydrophobic). Instead, it absorbs water (and any dissolved chemicals) directly through the leaves via osmosis.

However, these cases of polluted moss are extremely rare. I’m not trying to say that the moss in your backyard is harboring toxic chemicals that will make you get cancer. 

I’m guessing most likely, you probably don’t live in an area that’s heavily polluted. Even if you do, that’s probably not a problem you can mitigate by avoiding moss.

There are some claims that moss can cause skin irritation, but I couldn’t find any sources that directly identified the species of moss that cause it. 

However, I did find one article which says a type of fungal infection called sporotrichosis could be caused by a fungus that grows on plant matter (like sphagnum moss). But even then, it only occurs if it can enter the skin through a small cut or scrape.

Does Moss Cause Allergies?

I haven’t found any evidence that moss can cause an allergic reaction either through direct contact or through its spores.

It’s a common misconception that moss spores trigger allergies. Moss spores are actually non-allergenic

That doesn’t necessarily mean it’s impossible for moss to trigger allergies, but it’s extremely unlikely for most people.

What’s actually triggering the allergies is probably pollen which comes from trees, flowers, and fungi.

Although moss doesn’t cause allergies directly, it’s possible that the presence of moss can attract moisture which encourages mold growth. Mold actually can trigger your allergies.

If you find moss growing in a ventilation pipe, for example, it would probably be best to remove it so that it doesn’t encourage mold growth or cause other problems (which I’ve gone over in this article).

In case you do see “moss” being called out as an allergen, it’s possible that what’s being called out isn’t a true moss.

For example, I did see some sites point to sea moss as a potential allergen that can cause skin irritation. However, sea moss is technically a type of seaweed (algae), not a true moss. It falls under an entirely different taxonomic hierarchy.

I also saw that oak moss can cause an allergic reaction, but it’s technically not moss. It’s actually a lichen, which is a mix of algae and fungi. Those often do trigger allergies.

Long story short, a true moss probably won’t be the cause of your sudden allergy outbreak.

Can You Eat Moss?

You won’t find edible moss in your grocery store or by searching on Amazon, but most mosses can be eaten without any issues. 

In fact, moss has been used in herbal medicines as a diuretic. It’s also been used to treat coughs, inflammation, muscle cramps, and nausea. 

I haven’t eaten moss personally, but apparently, there are people who have. In this Reddit post, the taste is described as watery and muddy with a slight hint of broccoli. The Redditor didn’t feel any strange side effects afterwards, other than maybe having a dry throat for a few minutes.

Although it’s perfectly safe to eat moss, I wouldn’t recommend it for the same reason I wouldn’t recommend eating food off the floor. It’s probably unsanitary.

From a practical standpoint, moss won’t have many calories or provide much nutritional value. At the same time, you’re probably going to pick up chunks of the substrate (dirt, wood, bits of rock) along with the moss that the rhizoids have attached themselves to.

It’s also possible there may be insects living among the moss. A lot of insects are actually safe to eat, but I wouldn’t want to take any chances.

At the very least, I would probably want to give it a thorough rinse before attempting to take a bite out of the piece of moss you’ve found in your backyard.

Can You Drink Water That Passed Through Moss?

Although moss might be able to absorb some chemical compounds and provide some filtration, it won’t necessarily filter everything that could be floating around in the source of water

If you’re thinking about stream water, that can pose a serious risk of causing illness. You should never drink a natural source of water without first purifying it. There can be bacteria, parasites, and viruses swimming around in that water, even if it looks clean.

So just because you see some moss growing along the river, doesn’t mean you can start drinking river water. It’s always recommended to first pass the water through a water filter (which can filter out bacteria) or a water purifier (which can also filter out viruses).

However, if you know with complete certainty that the source of water is safe to drink, that source of water should still be safe to drink after passing through some moss. The moss will even provide a little extra filtration from bacteria in the water.

You can think about it like drinking water after eating moss. If the moss is safe to eat, then drinking water afterward isn’t going to cause you any harm. There’s no magical chemical reaction that’s going to create toxic compounds when water comes in contact with moss.

Is Moss Harmful In Any Way, Shape, Or Form?

To be completely transparent, there is actually one key scenario where moss could potentially be harmful.

That scenario is when you have moss growing on your roof.

But maybe not for the reason you might have thought when you first clicked on this article.

The reason moss growing on your roof could be harmful is because it can cause damage to your roof if left unchecked.

Since moss attracts and holds onto a lot of moisture, that moisture can wreak havoc on your roof over time as moss starts to wedge itself in between and under your roof shingles. It’s when moisture gets into these weak points that it can start to shorten your roof’s lifespan.

It can also clog up your gutters over time, which can cause water to start spilling over into areas it shouldn’t be.

So it’s not necessarily that the moss in and of itself can cause direct harm to your person via toxins or poisons, but it can cause you a huge headache when you start to see water leaking from the ceiling.

That’s why it’s usually recommended to give your roof a cleaning once every one or two years. Especially if you’re like me and live in a region where moss grows abundantly. Regular cleanings can prevent excessive buildup of moss growth and catch any problems early. 

In case you want to hear more details about when and why moss could damage your property, I wrote another article that covers all the scenarios where you might want to consider removing your moss.

Now that we’ve established that moss is completely non-toxic and harmless (when not growing on your roof) let’s take a look at the beneficial uses moss can have.

Can Moss Treat Wounds?

Moss is commonly known for its medicinal properties. It’s been used since the bronze age to treat wounds, most notably during the first world war, when cotton wound dressings were scarce.

There are two big reasons moss has been a popular treatment for wounds.

The first is that moss absorbs a lot of liquid. It can absorb up to 22 times its weight in water and 3-4 times more than cotton wound dressings. Over 90 percent of its cells are dead and empty for the sole purpose of being available to absorb water.

High water absorption is important in a wound dressing because it absorbs exudate (a mass of cells and fluids seeping from the wound) without drying out the wound, which provides better conditions for wound healing

The second reason moss can be used as a wound dressing due to its antiseptic properties. It chemically reacts with proteins, which allows them to completely immobilize bacteria and the enzymes excreted by invasive pathogens.

The only reason it isn’t used as much today to dress wounds is because it’s very labor-intensive to collect and prepare.

So you can definitely use moss to treat wounds if you ever find yourself lost in the wilderness without a medical kit handy. However, if you have the means, it’s probably best to just stick to using modern medical supplies.

Why Else Is Moss Useful To Humans?

Aside from medicinal uses, moss has a number of other indirect benefits for humans.

Like other plants, moss is another source of carbon sequestration. Just half a square meter of moss is able to absorb up to one kilogram of carbon dioxide per year. 

It’s a great carbon sink in no small part due to its large surface area to size ratio and high rate of photosynthesis. If you remember from your middle school biology class, photosynthesis converts carbon dioxide and water into sugars which will be stored as food for plants.

It’s also known to filter and retain water as well as stabilize the ground during rainy seasons. This helps minimize water runoff and erosion which can decrease soil fertility over time.

Peat moss, when decomposed, has also been used as one of the most popular, low-cost soil amendments. It forms over hundreds or thousands of years as it decomposes in waterlogged and oxygen-poor environments commonly found at the bottom of bogs. 

In fact, it’s so popular, that environmentalists are concerned that the current rate of peat moss harvesting will outpace the rate of renewal, leading to the destruction of peat bogs. 

There are current, ongoing efforts to increase the rate of renewal by transplanting live sphagnum moss back into recently harvested areas and spreading sphagnum spores to encourage growth of new moss.

Aside from environmental benefits, moss has also been used by humans for a variety of other purposes such as:

  • Shelter insulation – moss is a common material used during wilderness survival to keep impromptu blankets and shelters warm at night and cool during the day. It’s also been used to insulate the gaps in log cabins.
  • Warm clothing – in colder regions, moss has been used to keep boots and mittens warm
  • Fire tinder – dry moss is highly flammable and makes a great fire starter
  • Shelter waterproofing – moss is a strong water absorbent. Its dense network of leaves and stems will do a great job at prevent rainfall and dew from dripping into your shelter.
  • Camouflage – Moss is a great tool to camouflage your shelter or your clothing. It’s commonly used to create ghillie suits, the “moss costumes” military personnel, photographers, and hunters wear to conceal themselves in the wild

That list is by no means comprehensive. I’m sure if you browsed around online, you could easily come up with more.

I hope I’ve been able to convert you into a moss lover now that you know it’s completely harmless and has a bunch of beneficial uses. But I won’t blame you for hating moss that’s growing on your roof.