| Document and Entity Information | Feb. 24, 2022 |
| Cover [Abstract] | |
| Amendment Flag | false |
| Entity Central Index Key | 0001746466 |
| Document Type | 8-K |
| Document Period End Date | Feb. 24, 2022 |
| Entity Registrant Name | EQUILLIUM, INC. |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 001-38692 |
| Entity Tax Identification Number | 82-1554746 |
| Entity Address, Address Line One | 2223 Avenida de la Playa |
| Entity Address, Address Line Two | Suite 105 |
| Entity Address, City or Town | La Jolla |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 92037 |
| City Area Code | 858 |
| Local Phone Number | 412-5302 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock, par value $0.0001 per share |
| Trading Symbol | EQ |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | true |
| Entity Ex Transition Period | false |
