There are both religious and scientific reasons why people are advised to avoid milk during monsoon (Sawan) in India.

**Religious reasons:**

* In Hinduism, the monsoon season is associated with the god Shiva. Milk is considered to be a sacred offering to Shiva, and it is therefore avoided during this time.

* There is also a belief that milk can become contaminated during the monsoon season, as cows may eat contaminated grass or water. This can lead to illness, so it is advised to avoid milk during this time.

**Scientific reasons:**

* The monsoon season is a time of high humidity, which can create an ideal environment for bacteria to grow. This can lead to contamination of milk, which can make people sick.

* The monsoon season is also a time when there is a lot of flooding. This can lead to the contamination of water sources, which can also make milk contaminated.

It is important to note that there is no scientific evidence to suggest that milk is inherently harmful during the monsoon season. However, the risk of contamination is higher during this time, so it is advisable to take precautions.

Ultimately, the decision of whether or not to avoid milk during the monsoon season is a personal one. However, it is important to be aware of the risks and to take steps to protect yourself from illness.