In doccia uso prima lo shampoo e poi il balsamo.

In doccia is a very common idiomatic expression meaning in the shower / while showering.

• In doccia = the normal everyday way to say in the shower
• Nella doccia is possible, but it sounds more literal, as if you are emphasizing the physical place

So in this sentence, In doccia uso... means something like When I’m in the shower, I use...

Uso is the first-person singular present tense of usare.

• usare = to use
• uso = I use

Italian often drops the subject pronoun, so io uso is usually just uso because the verb ending already shows that the subject is I.

Italian masculine singular nouns usually take either il or lo as the definite article.

Lo is used before certain sounds, and shampoo is one of the words that takes lo, so you say:

• lo shampoo

You should learn this as a fixed combination: lo shampoo.

The article changes because the nouns begin with different sounds.

• balsamo starts with a normal b sound, so it takes il → il balsamo
• shampoo takes lo → lo shampoo

So the difference is not about meaning; it is about the sound and article pattern of each noun.

Italian uses definite articles more often than English.

So with everyday items or products, Italian commonly says:

• uso lo shampoo
• uso il balsamo

Even though English often leaves the article out, Italian usually includes it here. This is very natural Italian.

Prima means first, and here it works as an adverb.

Italian adverbs are often flexible in position, so:

• Uso prima lo shampoo... = I use shampoo first...
• Prima uso lo shampoo... is also possible

The version in your sentence sounds natural and common. It places the focus on the action uso, then adds the sequence word prima.

This is a very common Italian pattern for showing sequence:

• prima = first
• poi = then

So:

• prima lo shampoo e poi il balsamo = first shampoo and then conditioner

It is a very natural way to describe actions in order.

Sometimes yes, but poi is the most natural choice in this sentence.

• prima ... poi ... is a standard pairing
• dopo often means afterwards / later and can sound slightly different

So prima lo shampoo e poi il balsamo is the best everyday phrasing here.

Because usare takes a direct object in Italian, just like to use in English.

So you say:

• uso lo shampoo
• uso il balsamo

You do not need a preposition before shampoo or balsamo here.

Not always. Balsamo can mean different things depending on context.

In a sentence about showering and hair products, il balsamo clearly means conditioner or hair conditioner.

If you want to be extra specific, you can say:

• il balsamo per capelli = hair conditioner

But in everyday Italian, il balsamo is often enough when the context is clear.