The US has many grounds of inadmissibility, which are designed to keep the US safer. Grounds of inadmissibility include health reasons, such as the presence of dangerous and contagious diseases. Grounds of inadmissibility also include felony convictions and other reasons which may bar someone from the US. If you are not considered admissible to the US, however, you may still qualify to have these restrictions removed under 245A or 210 of the Immigration and Nationality Act. If this is the case for you, you can request to have grounds of inadmissibility waived in your case by filing USCIS Form I-690 (Application for Waiver of Grounds of Inadmissibility Under Sections 245A or 210 of the Immigration and Nationality Act).