Inclusion Criteria:
* Adolescent subjects aged ≥12 years and \<18 years, male or female.
* History of allergic diseases (self-reported is acceptable), including, but not limited to, food allergies, allergic rhinitis, allergic asthma, urticaria, and atopic dermatitis.
* Agreement to use effective contraception during the study and for 6 months after the end of the study.
* Subject and parent or legal guardian able to understand and voluntarily sign the informed consent form, and comply with study visits and related procedures.
Exclusion Criteria:
* Allergic to LP-003 or its excipients.
* Any serious or uncontrolled chronic disease (e.g., severe arrhythmia, ischemic heart disease, NYHA Class III/IV heart failure, severe pulmonary disease, inadequately controlled asthma, hypertension, diabetes, hypo- or hyperthyroidism) that may affect subject safety as determined by the Investigator.
* History of severe allergic reactions.
* Abnormal venous access, venipuncture or subcutaneous injection intolerance, history of needle or blood phobia.
* Estimated glomerular filtration rate (eGFR) \<30 mL/min/1.73m² at screening.
* ALT or AST \> ULN and considered clinically significant by the Investigator.
* Any other abnormal screening test result that, in the Investigator's opinion, could affect subject safety or study assessments.
* Systemic corticosteroid therapy (intravenous, intramuscular, or oral) within 4 weeks prior to study drug administration.
* Use of medications known to interact with epinephrine (e.g., β-blockers, ACE inhibitors, tricyclic antidepressants) within 4 weeks prior to administration.
* Use of biologic products (e.g., omalizumab) within 6 months prior to administration.
* Receipt vaccines within 14 days before administration or planning vaccination during the study.
* Participation in other clinical trials within 3 months prior to screening or within 5 half-lives of investigational product discontinuation (whichever is longer).
* Any other conditions that the Investigator considers subjects unsuitable for participation in the study.