Present habits with when (cuando)

To talk about habits, biological reactions, or things that happen consistently, use cuando (when) followed by the present tense.

When the boy sees blood, he faints.
Cuando el chico ve sangre, se desmaya.

You can start the sentence with cuando or put it in the middle.

I get dizzy when I am at heights, that's why I do not fly.
Me mareo cuando estoy en las alturas, por eso no vuelo.
My hands sweat when I am in a high place.
Mis manos sudan cuando estoy en un lugar alto.

Physical reactions

When talking about phobias or triggers, you will often use verbs for physical reactions. Notice how some of these, like fainting (desmayarse) or getting dizzy (marearse), are reflexive. Place the reflexive pronoun directly before the conjugated verb.

When I see blood, I get dizzy and I cannot speak.
Cuando veo sangre, me mareo y no puedo hablar.
When I clean the dust, I sneeze because I have an allergy.
Cuando limpio el polvo, estornudo porque tengo alergia.