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Are Highlighters Toxic to Dogs?

Are Highlighters Toxic to Dogs?

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Highlighters make reading through stuffy books much more convenient.

Can you imagine the hassle of perusing huge blocks of texts with nothing to help you pull out important information?

When working at the office or making personal notes at home, these colored markers come in handy in more ways than one.

But what happens when your lovely dog reaches for your highlighter pens and nibbles on them?

Should you worry?

And without mincing words…

Are Highlighters Toxic To Dogs?

The Short Answer:

Highlighters are made of ink and a plastic casing.

For the most part, the ink is somewhat toxic because it is made from alcohol and glycol ether.

According to Healthline, the ink can be mildly toxic especially if consumed in large quantities.

This means that your dog may be poisoned for nibbling on the highlighter, especially if they eat too much of the highlighter ink.

The casing can also cause issues for the dog if it leads to an obstruction.

To be on the safe side, consider using non-toxic highlighters. These are typically made with organic compounds e.g. using coconut oil instead of the glycol ether.

The Long Answer:

As we have already established, a highlighter is made up of a plastic casing and ink. Here is a detailed explanation of how they can cause issues for your Fido:

A. Ink

The highlighter ink is made from a range of chemicals including glycol solvent and water. These two make the bulk of it with a small percentage being the dye and a fluorescent pigment.

Although not all highlighters have it, some contain minimal amounts of biocide to inhibit the growth of bacteria and fungus.

The dyes used are pyrene-based, rhodamine, triphenylmethane, coumarin, xanthene, or a combination of any of them.

These chemicals are not meant for your dog’s consumption. Granted, they are available in small quantities but they are mildly toxic.

If they get to your dog’s stomach, they may trigger a stomach upset with symptoms such as vomiting and diarrhea.

The effects of the highlighter ink will depend on the amount ingested.

If the dog eats several highlighter pens or consumes an entire bottle of ink lying around somewhere, he may need medical treatment to get rid of the pollutants in his gut.

Additionally, puppies have weak digestive systems. Ingesting small amounts of the highlighter pen can cause more distress to them than adult dogs.

So, if you have a young dog, take extra caution around them.

B. Casing

Secondly, highlighters also contain a plastic casing surrounding the ink. This is where you should pay attention the most as it can spell trouble for your pooch.

For one, the casing can hurt your doggie’s mouth on its way to the stomach. This can happen if the dog eats the highlighter in haste and doesn’t adequately break the plastic apart.

The casing of the highlighter can also cause intestinal blockage. The reason is that it is made from plastic (either polythene or polyester beads).

When a dog ingests the highlighter, the plastic doesn’t come apart. Rather, it will go as it is down the throat and may cause bowel and other internal obstructions.

You can tell your pooch has intestinal blockage if he has vomiting, diarrhea, bloating, dehydration, nausea, weakness, stomach discomfort, restlessness, and loss of appetite.

For mild cases, you can try to induce vomiting at home by giving the pet a tablespoon of hydrogen peroxide through the mouth.

Encourage him to move around for some minutes. If nothing happens repeat the process twice more.

Rush him to the vet if there’s no vomiting all three times.

 If your dog suffers severe intestinal blockage, he will need surgical intervention to get rid of it.

Here are a few posts that you might find useful as far as inducing vomiting in dogs is concerned:

Can A Dog Die From Eating A Highlighter?

This is a yes and no question.

 In most cases, adult dogs don’t suffer ill effects after ingesting highlighters.

They will have upsets but if the ingested amount is not a lot, you can induce vomiting to get rid of the contents.

However, if the dog ingests lots of the plastic wrapping of the highlighter, things can go south really fast.

If not treated early, some cases of intestinal blockages can cause death within 3-7 days.

 The safest thing to do is to monitor the dog closely when he takes the highlighter.

In case of intestinal blockage symptoms, act fast to save the dog’s life.


Highlighters are great and all but they should be kept as far away from our pups as possible.

Both the ink and the casing can hurt your dog in many ways.

 If you cannot use the non-toxic type, keep the highlighters away from the reach of your dog.

In case of ingestion, contact your vet immediately.