Cambridge documents can’t/couldn’t help + -ing for being unable to control or stop an action, and also documents the separate “can’t help but + bare infinitive” pattern. Do not confuse the involuntary-action idiom with ordinary help meaning assist; the latter can take different complement patterns and expresses a different idea.
ReviewedEvidence1 sourceSectionEnglish Usage
Quick answer
Use “can’t help doing” when you mean you cannot stop yourself from an action; “can’t help to do” normally belongs, if used, to the separate help = assist sense rather than this idiom.
Key details
Confusion Familygrammar-and-usage distinction
Rule Familyverb complement pattern
TermsCan't Help Doing, Can't Help To Do
Further guidance
Boundary
Do not confuse the involuntary-action idiom with ordinary help meaning assist; the latter can take different complement patterns and expresses a different idea.
Construction
Cambridge documents can’t/couldn’t help + -ing for being unable to control or stop an action, and also documents the separate “can’t help but + bare infinitive” pattern.
Decision
Use “can’t help doing” when you mean you cannot stop yourself from an action; “can’t help to do” normally belongs, if used, to the separate help = assist sense rather than this idiom.
Sources and evidence
Sources are shown with the role they play in this guide. Historical or style-sensitive claims are kept within the evidence boundary described above.
Cambridge documents both admit + -ing and admit to + -ing for acknowledging something. Other passive patterns such as “be admitted to be” are separate constructions.
Both patterns are standard. “Advise waiting” recommends an action generally or in context, while “advise him to wait” names the person who is advised to perform it. A that-clause is another standard option.
When “afford” is followed directly by another verb, standard learner references use a to-infinitive: “afford to do.” An -ing form can appear elsewhere in a sentence, but it is not a like-for-like direct complement after “afford.”
“Agree to do” expresses consent to take an action. An -ing form normally follows a preposition in patterns such as “agree with doing,” which expresses approval rather than the direct promise-to-act construction.
Cambridge documents aim + to-infinitive for intention and aim at for directing effort toward an objective. Do not omit the preposition and present bare “aim doing” as equivalent to “aim to do.”
“Allow” can take an activity as its object, as in “allow smoking,” or a person/thing followed by a to-infinitive, as in “allow visitors to enter.” The patterns answer different structural questions: what is allowed versus who is allowed to do what.
