@My Dreams that sounds like a skin disease perhaps. That can come from many things, from tiny bugs to bacteria and such. Probably not a heat rash as it appears to affect the whole family. If flooding has happened over there then there could be a problem with bacterial skin infection. The doctor will need to look at it and assess what it is and then prescribe medicine for your whole family.
Unless God has directed you to seek prayers on the matter... you can ask for prayers from members here, but honestly that might show a lack of faith in the belief that God loves you and will heal you and your family from your own prayers together in a family group in prayer.
It is not advisable to leave that problem un-resolved. I know times might be difficult for you over in India as a Christian. If you cannot reach out for money aid from locals and local Christian churches then does the government have help for you? I don't know what type of health care your country has and am concerned it is not responsibly taking care of it's citizens. And that can be a problem with such a large population, but I was under the assumption that India was rich with money in the upper class level of society.
I will of course say a prayer for you and your family.