March 17, 2017: Is the shamrock toxic?

We boast of the green on our isle’s shores

Thanks to the plant that grows so grand.

It thrives in the mires, the bogs, and the mores.

The dear little Shamrock of Ireland.


            As St. Patrick’s Day approaches, the world looks to celebrate the Irish culture with international festivals, parades, dancing, special foods, and the “wearing of the green”.  One traditional symbol of St. Patrick’s Day is the Shamrock, which was chosen as Ireland’s national emblem based on legends of its use by St. Patrick.  The Shamrock is a common name given to several different types of three-leafed clovers native to and plentiful in Ireland.  Although most commonly associated with yellow clover or white clover, the exact type of plant that represents the “true” Shamrock remains a mystery.  Several different varieties of clover exist in the United States.  Some are native to the continent, while others have been naturalized to North America, originating in Europe and Asia.  How harmful are the “Shamrocks” found in the USA?  Should we be concerned for individuals who place sprigs of “Shamrocks” in their beverages and then drink a toast to this Irish holiday?

            A brief overview of the potential toxic effects that could develop from the different genera of clover will best answer this question. Some of the common types of clover found in this country include:

  1. The Crimson or Italian Clover (Trifolium Incarnatum), which is considered non-toxic and symptoms from ingestion or dermal exposure are unexpected.
  2. The Purple Prairie Clover (Petalostemum Purpureum), which is also considered non-toxic and symptoms from ingestion or dermal exposure are unexpected. 
  3. The Pink Clover (Dianthus Species), which contains an irritant compound that could result in eye, mouth, throat, skin, and gastrointestinal irritation upon contact or ingestion.
  4. The Stinking Clover (Cleome Serrulata), which contains an irritant, Glucocapparin, that could cause eye, mouth, throat, skin, and gastrointestinal irritation as well as an allergic reaction with contact or ingestion.
  5. The Red Clover (Trifolium Pratense), which can cause “slobbering sickness” in animals with bloating, stiffness, diarrhea, and emaciation, but human cases have not been seen.
  6. The Sweet Yellow Clover (Melilotus Officianalis) and the Sweet White Clover (Melilotus Alba), which contain dicumarol and have caused hypoprothrombinemia in animals.  Large ingestions could lead to a warfarin effect with the risk of bleeding.
  7. The White or Dutch Clover (Trifolium Repens), which has moderate cyanogenic capabilities, but no cases of cyanide poisoning have been reported.  However, large ingestions could possibly cause dyspnea, weakness, dizziness, and cyanosis.

Thus, based on this synopsis, severe toxicity from the ingestion of a small amount of clover residue that might be in a beverage is unlikely; however gastrointestinal upset could develop. Of course, if someone eats a large quantity of the more dangerous clover species, then serious side effects could arise.  As always, please contact the poison control center for any questions or concerns that might surface during the St. Patrick’s Day festivities.

For each petal of the shamrock

This brings a wish your way

Good health, good luck, and happiness

For today and every day

-Mary Elizabeth Blake-



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This Question prepared by:  Cheri Wessles, CSPI, MBA


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Donna Seger, MD

Medical Director

Tennessee Poison Center

Poison Help Hotline: 1-800-222-1222