Short answer: no, teaching two languages doesn't cause lasting confusion. There's often a brief period of mixing early on — and that's normal, not a red flag.
What the research actually shows
Bilingual children consistently reach reading outcomes comparable to monolingual peers over time. There's often a brief early stage where sounds or words from the two languages mix — this reflects a child still sorting out which rules belong to which language, and it resolves naturally with continued exposure to both.
A possible advantage, not just a neutral outcome
Some research suggests bilingual children develop stronger general phonological awareness — the skill of noticing and manipulating sounds — because they're already comparing how two sound systems work against each other. This is the same skill our phonological awareness activities guide builds directly.
The practical approach: teach each language on its own terms
Teach each language's letter-sound rules within that language's own context, rather than trying to merge the two systems into one lesson. English phonics should be taught as English phonics — our full 43-phoneme map and blog content are built specifically around English's own sound system.
If English specifically is the second or additional language, our phonics for ESL kids guide covers which English sounds tend to be hardest depending on the child's first language.