Importance of conch (Sankh)
According to Hindu belief, no puja, havan, yagna etc. is considered complete without the use of conch shells. According to religious scriptures, by blowing conch shells, ghosts, ignorance, disease, mistreatment, sin, downtrodden thoughts and poverty are destroyed. The tradition of playing conch has been going on since ancient times. In the Mahabharata period, Shri Panchajanya conch was played many times by Shri Krishna. According to modern science, by playing conch shell exercise our lungs, we get power to fight respiratory diseases. At the time of worship, the water kept in the conch is sprinkled all over it, which has the wonderful power to destroy germs in the conch water. Also, drinking water kept in conch shell is very beneficial for health and our bones, teeth. The shell has the properties of calcium, phosphorus and sulfur which get into the water kept in it.
And remember one special thing always, do not offer conch (Sankh) water on Lord Shiva!
Why do not offer water to Shiva by conch( sankh) ?
According to Shiva Purana, there was a Mahaprakrami monster named Shankhchud. Shankhchud was the son of Daityaraj Dambha. When no child was born to the Daityaraja Dambha for a long time, he did intense penance for Vishnu and appeared pleased with austerity. Vishnu asked to ask for a boon , then Dambha asked for a mahaparakrami invincible boon son's for all the three places and Vishnu were disappeared by speaking thaastu.
Then Shankhchud was born in Dambha and he pleased Brahma at Pushkar by doing severe penance. Brahma asked for the boon and Shankhchud asked for the boon to become invincible to the gods. Brahma speaks thaastu and gave him Sri Krishna's armor, then he disappeared. While going, Brahma ordered Shankhchud to marry Tulsi, the daughter of Dharmadhvaja. Tulsi and Shankhchud got married after getting Brahma's orders.
Daityaraja Shankhchud established ownership over the three worlds under the head of Brahma and Vishnu's boon . The gods were distressed and sought help from Vishnu, but they themselves had granted the gift of such a son to Dambha, so they prayed to Shiva. Then Shiva decided to end the sufferings of the gods and they left.
But due to Shri Krishna Kavach (armor's) and Tulsi's integrity, Shivji was not able to kill him, then after taking Brahmin form from Vishnu, received in donation his Sri Krishna armor from Daityaraja and then the took form of Shankhchud and kidnapped Tulsi's modesty.
Now Shiva consumed Shankhchud with his trident and Shankh was born from his bones. Since Shankhchud was a devotee of Vishnu, Lakshmi-Vishnu is very fond of conch water and there is a law to offer conch water to all the gods. But since Shiva killed him, the water of the Conch (Sankh) is said to be prohibited to Shiva. That is why Shiva is not offered water from the conch (Sankh) .