Why do lord Shiva drink Cannabis?

Lord Shiva – One of the major dimities (Trimurti) is also known as lord of Bhang (Cannabis).
Lord Shiva use to have Bhang to keep his body temperature down. Bhang is supposed to be a coolant. It lowers down the body’s metabolism and that brings the overall body temperature down. Same is the case with Marijuana and Datura.
You can relate this from the story of Samnudra Manthan.
The Dev (gods) and Rakshasas (demons) got together for the colossal task of churning the cosmic ocean. Mount Mandara, was used as the pole to stir the waters. And Vishnu’s Koorma Avatar (Tortoise) balanced the mountain on its back. The great serpent Vasuki was used as the churning rope. As the ocean was churned lot of goodies came out of it which the Devas and Rakshasas distributed amongst themselves. But from the depths of the ocean also came out the “Kalkoot” visha (poison). When the poison was taken out, it started heating up the cosmos considerably. Such was its heat that people started running in dread, animals started dying and plants started withering. The “Visha” had no taker hence Shiva came to everyone’s rescue and he drank the Visha. But, he did not swallow it. He kept the poison in his throat. Since then, Shiva’s throat became blue, and he came to be known as Neelkantha or the blue-throated one.
Now this caused immense heat and Shiva started getting restless. A restless Shiva is not a good omen. Hence the gods undertook the task of cooling Shiva off. According to the legends, Chandra Dev (Moon god) made Shiva’s hair his abode to cool him and that Shiva moved to Kailash (which has subzero temperatures all year round) after the Samudra Manthan. Shiva’s head was covered with “Bilva Patra”(Beel Patra). So you see everything was being done to cool Shiva off.
In addition, Lord Vishnu dropped drops of Amrita (the drink of immortality) at four places, while transporting it in a kumbha (pot). These four places are identified as the present-day sites of the Kumbh Mela. The places are Haridwar, Nasik,  Ujjain and Allahbad.

SIGNIFICANCE OF BHANG
Offering bhang to Shiva is symbolically saying this: “Oh Mahadev! I offer all intoxication within me to you in the form of Bhang. I offer you my intoxication related to maya, women, fame and all bad habits. Just as you consumed the kaalkoot (visha) during the Samundra Manthan, be gracious enough to accept my intoxication and bless me with purity, knowledge and humanity”.

MEDICINAL VALUE OF BHANG
If taken in the right quantity it can cure problems like dysentery, phelegm etc and quicken digestion leading to weight loss.
It can cure arthritis, and normal issues like vomiting, nausea, fever, sunstroke.
Applying a paste of it cures chapped and rough skin.

EFFECTS OF OVERDOSE
If taken in access amount Bhang can pump the heart rate up, cause psychosis and blood pressure.
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