Normally, every syllable in English must have at least one vowel (or vowel sound). So it’s quite surprising to think that there are words with 5 or more consonants in a row.
Here are a few words with 5-letter consonant strings:
BIRTHPLACE, BREASTSTROKE, DOWNSTREAM, EIGHTHS, MATCHSTICK, NIGHTCLOTHES, NIGHTCLUB, NIGHTDRESS, STRENGTHS, THOUSANDTHS
Here are two words with 6 consonants in a row:
Can you think of any more? There are quite a few.