Once picked up, Tick can't be dropped or replaced with another trinket.
Notes
Only works on the first stage of multistage bosses.
Friendly enemies are also affected by the health removal when above 60 hp.
This trinket's effect can be multiplied to a maximum of x2 through any combination of multiple copies and Mom's Box. This also includes multiplying the healing effect when entering a Boss Room.
This trinket's effect can be stacked via any combination of multiple copies, golden variants, and Mom's Box with enough stacks causing any enemy above 60 hp to have the lowest amount of health possible with any amount of damage killing them. This also includes stacking the healing effect when entering a Boss Room. The HP removal stacking effect is equal to 0.85 ^ Number of Tick Instances, with golden trinkets adding on 2 to this.
Golden Trinket: The golden version can be freely dropped or replaced by another trinket.
Marbles / Smelter / Gulp!: Absorbs the trinket, allowing Isaac to pick another trinket up.
Match Stick: Tick can be removed by picking up Match Stick.
Match Stick + Mom's Purse / Belly Button: Match Stick can no longer remove Tick, instead moving to the second trinket slot even if Isaac already holds two trinkets.
Being able to replace the Tick with Match Stick is a reference to how one can remove a tick that has latched onto their skin in real life with a heated tip of a match stick; however, removing a tick like this can expose oneself to disease-causing bacteria present in the tick. It is also a feature that was carried over from the original The Binding of Isaac, though it's unclear why it wasn't originally added in Rebirth.
The Tick is the only trinket that passively changes Isaac's appearance.
The Tick bears similarity to a real-life deer tick.
Red Heart if he enters an unexplored 
Boss Room.
Friendly enemies are also affected by the health removal when above 60 hp.
This trinket's effect can be multiplied to a maximum of x2 through any combination of multiple copies and 
Mom's Box. This also includes multiplying the healing effect when entering a 
This trinket's effect can be stacked via any combination of multiple copies, golden variants, and 
Golden Trinket: The golden version can be freely dropped or replaced by another trinket.
Marbles / 
Smelter / Gulp!: Absorbs the trinket, allowing Isaac to pick another trinket up.
Match Stick: Tick can be removed by picking up Match Stick.
Mom's Purse / 
Belly Button: Match Stick can no longer remove Tick, instead moving to the second trinket slot even if Isaac already holds two trinkets.
The Binding of Isaac: Rebirth
