The use of milk thistle has been around for more than 2000 years, and there is a strong historical background behind the use of milk thistle extract. Milk thistle has been cultivated throughout Europe and is widely popular in Greece, Italy, and Germany. Their ancestors used this herb to treat liver, kidney, spleen and gallbladder issues. Milk thistle is also used to treat serpent bites and mushroom poisoning. Today, even scientists agree that milk thistle has unique anti-inflammatory properties that can help to flush out toxins from the liver.

However, side effects are typical for any drug- be it over the counter drugs, prescription medication or herbal supplements. Most of the prescription drugs have a lengthy list of side effects, but thankfully, there are only a few issues associated with this milk thistle herbal tea.

Here is a list of the some of the potential side effects of milk thistle extract. Should you face any of these, discontinue the use of the herb for at least three days. Furthermore, it is advised to buy all supplements from a reliable and renowned seller. If the milk thistle is of inferior quality, many side effects can occur due to chemical pollution and not the actual compounds of the herb itself.

1- Might cause abdominal issues

One of the most well known side effects caused by milk thistle is an upset stomach. According to some research, milk thistle may not suit everyone, and it can cause loss of appetite and abdominal bloating in its users. Other less common side effects are intestinal gas, indigestion, and even diarrhea in rare cases.

2- May cause allergic reactions

Milk thistle belongs to the family of Asteraceae or Compositae. So, if you are allergic to ragweed, marigold, daisies, and chrysanthemums- then you could also experience an allergic reaction with the use of milk thistle. Research confirms that milk thistle might cause an allergic reaction to some of its users that can result in skin rashes, hives or an occasional breakout of eczema.

This is why if you experience an itching sensation after ingesting the herb, stop using it immediately and consult your local doctor. Skin rashes occur because your immune system is not accepting the herb and builds a defense mechanism against the supplement.

3- Can interact with estrogen

Known for its estrogen-like properties, milk thistle can worsen certain health conditions which are sensitive to estrogen levels, such as breast cancer, uterine cancer, endometriosis or uterine fibroids.

Few compounds in milk thistle begin to mimic the physiological functions of estrogen due to which hormone-sensitive conditions can worsen over the period.

Apart from its estrogen-mimicking properties, it can also decrease the hormone levels in the body. This is why you shouldn’t take it along with estrogen pills, and it can reduce their effectiveness.

4- Can interact with cholesterol medication

One important fact to remember is that always consult your doctor before taking any herbal supplement. Milk thistle may interfere with some allergy drugs, high cholesterol medication, and anti-anxiety drugs. Some lipid-lowering drugs like Mevacor, Lescol, Zocor, Pravachol, and Baycol are affected by the intake of milk thistle extract. According to research, the reason behind this interference is that the same liver enzymes digest both milk thistle and the medications mentioned above. Hence, affecting the performance of cholesterol medication.

5- Might lower blood sugar way too much

The main component of milk thistle, Silymarin Marianum, is an antioxidant and a natural remedy to maintain blood sugar levels. Research has proven that milk thistle can dramatically reduce the fasting blood sugar levels in diabetic patients.

However, if you are already undertaking medication to maintain your blood sugar levels, then milk thistle may lower your blood sugar levels far too much.

6- Can have interactions during breastfeeding and pregnancy

Pregnancy and motherhood can fill you with wonder and awe, but it can also make you question many little things. It is good to be overly concerned regarding herbs and nutrition because everything you eat or drink is going to affect the baby.

Many herbs must be taken with caution especially during pregnancy and breastfeeding. Unfortunately, there are not many scientific studies that can confirm the benefits of milk thistle extract during pregnancy and breastfeeding. There is an animal study which shows that the herb increases prolactin in the body and stimulates milk production, but it is recommended to take the herb in supervised doses or skip it altogether.

7- Might interact with anti-allergy and anti-anxiety drugs

The liver breaks down most pharmaceutical drugs, and milk thistle might affect this process. This is why, if you are taking certain allergy drugs, high cholesterol medication and anti-anxiety drugs then milk thistle might increase their side effects or hinder their performance.

Some of the drugs affected by milk thistle include Valium, Lescol, Cozaar, Xanax, and Zyflo.

8- Can cause weakness

Many people experience physical weakness after the intake of milk thistle extract. Other side effects include a tingling sensation in the muscles and muscular cramps. A few people have also experienced excessive sweating and weakness after regular use of milk thistle. So, it is advised to monitor your body vitals for a few days after introducing milk thistle in your daily regime.


Most researchers claim that milk thistle intake does more good than harm. There is insufficient research to support the side effects of milk thistle tea, and most of them occur in sporadic cases. It is proposed that you consult your doctor before deciding to take any herb regularly, and the same applies to milk thistle.

If you are unsure about the many benefits of milk thistle, you’ll be surprised to know that US National Institutes of Health and National Library of Medicine has cataloged over 400 scientific research studies dedicated to the wonders of milk thistle and its active compound, silymarin. These studies have reaffirmed the traditional benefits of milk thistle. It has been used for centuries; so don’t let a few side effects shake your belief in this magical herb. Talk to your doctor and try it out for yourself.

Have you used milk thistle extract before and experienced any side effects? How did this herb affect your body? Let us know in the comments below, and inspire your fellow readers with your story.

Share this Post