Electronic – Relay contact (switching) voltage

When the relay opens it will draw an arc. With AC power the current drops to zero 100 or 120 times per second (depending on whether you have 50Hz or 60Hz power), and this will allow the arc to extinguish. With DC power you don't get this automatic interruption, and an opening arc may last longer, burning the contacts in the process. That's why relays are allowed to switch only a fraction of the AC power if DC.
It's not uncommon to see 250V AC relays only rated for 30V DC.

The problem with DC over about 40V is that an arc can form much more easily, compared to AC where the 'zero-crossing' provides 100/120 opportunities per second (assuming 'mains') for the initial arc that can occur at the instant of disconnection to extinguish itself.

DC relays are always more expensive at a given current-capability compared to AC, because they need to separate the contacts further to achieve the same current interrupting capability.

Relay voltage ratings are also about insulation materials types, thicknesses, & distances between the contacts and the coil, so even though your circuit may have some mA-scale limited current capability, there's still potential for arc between contacts & coil, depending on how well or poorly the 24VDC-rated relay is designed & manufactured. I really would recommend going for a relay rated for what you're doing.