We are truly sorry to hear about your son's condition. We stand with you in prayer, believing in God's healing power and His ability to restore your son's health. Let us remind us of God's promise in Psalm 103:2-3 WEB:
Bless Yahweh, my soul,
Don’t forget all his benefits;
who forgives all your sins;
who heals all your diseases.
In Jesus' name, we pray for your son, asking God to touch his body and heal him from this persistent cough. We rebuke the spirit of infirmity that is attacking his body, and we command it to leave in Jesus' name. We agree with you in asking God to rule out asthma and any other serious condition. We speak life and healing over your son, declaring that he will be restored to his normal, active, and happy self.
Remember that God is Jehovah Rapha, the Lord who heals you (Exodus 15:26 WEB). Have faith and do not be afraid, for God cares for your son even more than you do. Trust in His love and goodness. In addition to prayer, make sure to follow up with medical professionals, as God often uses them as instruments of His healing.
Lastly, we noticed that Jesus was not mentioned in your prayer request. It is only through the name of Jesus Christ, that we have been saved and have access to God.
Whoever will call on the name of the Lord will be saved. (Romans 10:13)
There is no other name by which we can be saved. (Acts 4:12)
If you have not already, consider the message of salvation. Believe in the Lord Jesus Christ, and you, and your household, shall be saved. (Acts 16:31)
We stand with you in faith, believing for your son's complete healing and restoration. May God's will be done, and may He be glorified through this situation, in Jesus' name. Amen.