| Document and Entity Information | Mar. 24, 2021 |
| Cover [Abstract] | |
| Amendment Flag | false |
| Entity Central Index Key | 0001711279 |
| Document Type | 8-K |
| Document Period End Date | Mar. 24, 2021 |
| Entity Registrant Name | KRYSTAL BIOTECH, INC. |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 001-38210 |
| Entity Tax Identification Number | 82-1080209 |
| Entity Address, Address Line One | 2100 Wharton Street |
| Entity Address, Address Line Two | Suite 701 |
| Entity Address, City or Town | Pittsburgh |
| Entity Address, State or Province | PA |
| Entity Address, Postal Zip Code | 15203 |
| City Area Code | (412) |
| Local Phone Number | 586-5830 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock |
| Trading Symbol | KRYS |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | true |
| Entity Ex Transition Period | true |
