| Document and Entity Information | Mar. 11, 2021 |
| Cover [Abstract] | |
| Amendment Flag | false |
| Entity Central Index Key | 0001341235 |
| Document Type | 8-K |
| Document Period End Date | Mar. 11, 2021 |
| Entity Registrant Name | ALDEYRA THERAPEUTICS, INC. |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 001-36332 |
| Entity Tax Identification Number | 20-1968197 |
| Entity Address, Address Line One | 131 Hartwell Avenue |
| Entity Address, Address Line Two | Suite 320 |
| Entity Address, City or Town | Lexington |
| Entity Address, State or Province | MA |
| Entity Address, Postal Zip Code | 02421 |
| City Area Code | (781) |
| Local Phone Number | 761-4904 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock, $0.001 par value per share |
| Trading Symbol | ALDX |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
