Final answer:
The nurse must consider the presence of signs of child abuse and take a thorough history to assess the welts and scars on a toddler. Food allergies and a history of chickenpox are less likely to be relevant in this case. Suspected child abuse should be thoroughly investigated, with appropriate referrals made.
Step-by-step explanation:
When a nurse in the emergency department observes large welts and scars on the back of a toddler admitted for an asthma attack, they must consider differential diagnoses, but given the physical findings, the nurse must also consider signs of child abuse as part of the assessment. It is imperative to take a thorough history, encompassing any prior injuries that may explain the scars and the context of the asthma attack. Additionally, while food allergies can present with skin manifestations and exacerbate asthma, the pattern and nature of welts and scars described would not typically result from allergic reactions. Finally, a history of chickenpox could provide explanations for scarring but would not normally cause large welts.
The nurse's assessment should thus prioritize the possibility of non-accidental trauma. Inquiries about the history of the scars, behavioral changes in the child, or inconsistent stories from caregivers could all contribute to a complete assessment, and referral to appropriate services including social work and child protection may be warranted if abuse is suspected.