Necesito una horquilla porque se me cae el pelo en la cara.

In Spain, una horquilla usually means a bobby pin / hairpin used to hold hair in place.

A useful regional note:

• In Spain, horquilla is very common for this.
• In other Spanish-speaking countries, people may say things like pasador, gancho, or something else depending on the region.

So for Spain, this word is perfectly natural.

Because horquilla is a feminine noun.

So:

• una horquilla
• la horquilla

The ending -a often suggests a noun is feminine, and here that pattern works.

Because here porque means because, so it is the conjunction that gives a reason.

Compare:

• porque = because
• por qué = why
• el porqué = the reason / the why
• por que = a less common combination in certain structures

In this sentence, the speaker is giving a reason, so porque is correct.

Here se me cae means something like it keeps falling / slipping for me, or more naturally in English, it falls or it keeps getting into.

So se me cae el pelo en la cara means the hair is falling into the speaker’s face in a way they are experiencing or being affected by.

This structure is very common in Spanish when something happens to someone, often unintentionally:

• Se me cayó el vaso = I dropped the glass / the glass fell on me
• Se me olvidó = I forgot
• Se me rompe = it breaks on me

It often sounds more natural in Spanish than a direct English-style wording.

They do different jobs:

• se is part of the verb idea here: caerse, which often suggests something falls/slips accidentally or ends up falling
• me means to me / on me, showing who is affected by it

So se me cae el pelo is not literally reflexive in the English sense. It is more like:

• the hair falls on me / keeps falling for me
• natural English: my hair keeps falling

This is one of those Spanish patterns that is better learned as a whole.

Because Spanish often uses the definite article with body parts when it is already obvious whose body part it is.

So Spanish prefers:

• se me cae el pelo
• me duele la cabeza
• me lavé las manos

rather than always using:

• mi pelo
• mi cabeza
• mis manos

Since me already shows who is involved, el pelo sounds natural.

In Spanish, pelo is often used as a singular mass noun when talking about someone’s hair in general.

So:

• el pelo = hair in general
• los pelos = individual hairs, or sometimes hair in a more countable sense

In this sentence, the speaker means their hair as a whole, so el pelo is the normal choice.

They are very similar, but not always identical in tone.

• pelo = the everyday, very common word
• cabello = also means hair, but can sound a bit more formal, careful, or stylistic

In casual speech in Spain, pelo is completely normal here.
If you said cabello, it would still be understandable, but it might sound a little less everyday in this sentence.

For the same reason as el pelo: Spanish often uses the definite article with body parts instead of a possessive.

So:

• en la cara
• en los ojos
• en la frente

rather than:

• en mi cara
• en mis ojos
• en mi frente

Because the sentence already makes it clear whose face it is, la cara sounds natural.

Literally it is in/on the face, but the natural English meaning here is in my face.

With hair, en la cara is the normal Spanish way to express that it falls forward and bothers you around the face area.

English and Spanish do not always divide space in exactly the same way, so this is best learned as a natural expression:

• se me cae el pelo en la cara = my hair keeps falling in my face

Yes — by itself, se me cae el pelo can often mean my hair is falling out.

That is why en la cara matters so much here. It changes the meaning clearly:

• Se me cae el pelo. = My hair is falling out. / I’m losing hair.
• Se me cae el pelo en la cara. = My hair keeps falling into my face.

So the extra phrase removes the possible ambiguity.

Some variation is possible, but the pronouns must stay with the verb in the correct way.

Natural options include:

• se me cae el pelo en la cara
• el pelo se me cae en la cara

Both are possible, but the version in your sentence sounds very natural and conversational.

What you cannot do is move the little pronouns randomly. Spanish clitic pronouns like se and me have fairly strict placement rules.