When should you not eat mussels and why | how to tell if they are bad or not

Fresh black mussels before cooking
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So, you might think it’s okay to eat black mussels all year round! There is an old saying that mussels should only be eaten in the months that have an R in the spelling, and that includes September through April. This is only true for the Northern Hemisphere. 

When should you not eat mussels in a nutshell:

  • You should avoid mussels during the summer months
  • Check the shell of the mussel. Only shells that are still sealed before being cooked should be eaten. 
  • If the shell is cracked or damaged, it should not be eaten but discarded. An open or cracked shell indicates a dead mussel inside.

How to tell if mussels are bad

How to tell if fresh mussels are bad

Mussels are a delicacy appreciated all over the world. Mussels belong to various families of bivalve molluscs. They can be recognised by their elongated shell and asymmetrical shape. Mussels contain very useful fats, the long-chain fatty acids EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid), and are an excellent source of vitamins. 

Fresh mussels have a faint ocean-like flavor with mushroom accented undertones that are slightly sweet. 

I bought these mussels directly from a local on the Croatian coast. You can’t get them fresher than these:

After purchasing fresh mussels, wash and store or even better freeze them as soon as you arrive home if you do not intend to prepare them immediately. If you want to know how to freeze mussels at home, check my post here!

Bear in mind, though, that mussels have a short shelf life. Cook the mussels within two to three days of purchasing them for optimal freshness. 

When you buy fresh mussels, there are a few telltale signs that the mussels are not fresh. First, smell the mussels. A smell is a clear sign that the mussels are not fresh. A fishy smell is what you need to look out for. 

If there are partially open mussels, lightly press the shell closed. If the mussel does not close, it’s dead and it is best to discard the mussel. 

Ideally, mussels should smell slightly fishy and salty. Also, all shells should be closed. 

How to tell if cooked mussels are bad

Some individuals have stated that mussels smell like sewage, while others say mussels smell like poop when the mussels are off. 

Mussels are cooked by steaming. This process releases the liquid contained in the mussel. Therefore, no additional water is required. In addition, cooking mussels kills them and relaxes the muscle that keeps the shell closed. 

Therefore, if the shell opens up after cooking, this proves that the mussel was alive; if not, the mussle is bad.

Male mussels are pale white when cooked, while female mussels are more of an orange hue. During the steaming process, the shell of the mussels will open, which indicates that the mussels are done. 

Mussels that do not open during cooking should be discarded.These mussels are dead and not suitable for consumption. Also, cooked mussels are bad if the mussel floats after cooking.

Is it okay to eat mussels that are slightly open

There is a myth that mussels are off if they are open before cooking. This may be true, but chances are, the mussel may still be alive. An easy test is to tap on the shell or the bowl. 

Mussels that are still alive will close their shell. If the shell doesn’t close after you have tapped it or the bowl, it is best to discard it. 

Can you eat mussels that are cracked

The shell of a mussel is quite delicate. During transport, it is likely that the shell may be cracked or damaged. Mussels whose shells are cracked or badly damaged are probably dead. Sometimes, however, badly damaged mussels may still be alive.

Cooking the mussel is the only way to be sure it is still alive. If the mussel opens during cooking, it is fit to eat. Eating dead mussels or mussels whose flesh have already spoiled increases the risk of food poisoning, infectious diseases, contamination by microorganisms, and other health problems.

Should I throw away cracked mussels

Mussels that have a cracked or have a damaged shell should be discarded. However, as mentioned before, shells may be cracked during transportation due to the delicateness of the shell. 

Why are mussels that are open, bad mussels

Open shellfish such as mussels may be dead. But, tapping it lightly should determine if it is still alive. If the mussel is in fact dead, eating it can be very dangerous to your health. If the mussel is dead, the deterioration of the mussel’s meat has already begun. In addition, mussels consume algae. These algae produce many toxins. The toxins build up in the flesh of mussels, and this poses great danger to anyone consuming the shell fish.

Contaminated shellfish can lead to various illnesses, such as food poisoning, to name just one. The symptoms that result from eating contaminated shellfish occur relatively quickly. 

Between 30 minutes and 15 hours after eating contaminated shellfish, the first symptoms appear around one to two hours after consumption. Recovery occurs within three days after eating the shellfish.

How to tell if mussels are dead

Dead mussel, is a bad mussel. Bacteria grow rapidly at temperatures between 40 °F and 140 °F. Mussels left at room temperature for more than two hours should be discarded. An interesting fact is that mussels left under tap water for more than 15 minutes will die. If you add water when cooking clams and some clams float, they are either dead or empty.

If mussels do not open when boiled or steamed, they are dead. On the other hand, mussels that open before cooking may also be dead. Mussels that have cracks or breaks or are badly damaged may also be dead.

What happens if you eat dead mussels

Eating dead shellfish can lead to various illnesses such as food poisoning, contamination by microorganisms, and other health problems. 

Symptoms appear relatively quickly and may include nausea, diarrhea, and vomiting. These symptoms are followed by numbness in the mouth, dizziness, headache, and hot and cold fever.

Almost all shellfish contain E.coli to some extent. Poisonous shellfish contain the very dangerous neurotoxin saxitoxin, which can also cause paralysis. Paralytic shellfish poisoning (PSP) is a result of the neurotoxin. Symptoms include numbness of the mouth and lips, which quickly spreads to the face and neck. In extreme cases, consumption of contaminated shellfish will kill you.

Mussels also ingest bacteria that are largely harmless to them, but dangerous to humans who consume the contaminated mussels. As previously mentioned, the algae cause toxin build-up in the flesh of the mussel, which is hazardous for consumption. 

What do bad mussels taste like

Mussels that have died begin to smell. This is because the mussel has already begun to rot. Some have described the smell as similar to sewage or poop, for lack of better descriptions. In addition, the mussels can smell very fishy. Again, this is a clear sign that the mussel is not fresh.


Mussels should be prepared immediately after purchase. When mussels are transported to the fish market or fishmonger, their delicate shells may be damaged. This is not always a sign that the mussel is dead. Mussels that are open before cooking and mussels that are closed after cooking should preferably be discarded, as this is a sign that the mussel is dead.


I am a kind of person that would sneak a taste out of grandma’s pot when I was barely tall enough to reach it. I grew up in kitchens full of love and liveliness and have spent my whole live learning, experimenting and succeeding in the art of cooking. At Pro Family Chef, every day is an opportunity for a new meal and a brand new flavor. I created this website to connect people that love to cook, with the products designed to make their cooking easier, hassle-free and rewarding every time.

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