A Phase 1, Randomized, Placebo-controlled, Dose-escalation Safety Study of MEDI4212 in Subjects With IgE >= 30 IU/mL

Inclusion Criteria: * Age 18 through 60 years * Written informed consent and any locally required authorization * Body weight 45-150 kilogram (kg) for Cohorts 1-3, 4b, and 5-9. Body weight 45-90 kg for Cohort 4a * Females must have been surgically sterilized or postmenopausal * Non-sterilized males who are sexually active with a female partner of childbearing potential must use a highly effective method of contraception from Day 1 through Day 85; Both partners to use contraception * Sterilized males must be at least 1-year post vasectomy or use a highly effective contraceptive method * Healthy Japanese population as determined by a responsible physician * Current diagnosis of allergic rhinitis, allergic asthma, or atopic dermatitis (cohorts 1-6) with a diagnostic immunoglobulin E (IgE) of 30 international units per milliliter (IU/mL) at Screening. Diagnostic IgE levels are further restricted for subjects enrolling into each cohort, with the following levels required at Screening: Cohorts 1 and 2: 30-700 IU/mL; Cohort 3: 30-700 IU/mL (4 subjects), greater than (\>) 700-1,200 IU/mL (4 subjects), and \>1,200 IU/mL (4 subjects); Cohort 4a: 30-500 IU/mL; Cohort 4b: \>700 IU/mL; Cohorts 5 and 6: 30-700 IU/mL (4 subjects per cohort) and \>700 IU/mL (6 subjects per cohort) or Japanese Cohorts 7-9: greater than or equal to (\>=) 30 IU/mL * Nonsmoker for \>=6 months * Obsolete criteria as no longer require Positive in vitro IgE fluorescence enzyme immunoassay (FEIA) response * A forced expiration volume in one second (FEV1) \>= 80 percent (%) predicted in subjects with asthma. Non-asthmatic subjects with FEV1 \>=80% predicted, or with FEV1 less than (\<) 80% predicted but who, in the opinion of the investigator, do not have lung disease * Ability and willingness to complete the follow-up period through Day 85 as required by the protocol. Exclusion Criteria: * Any condition that, in the opinion of the investigator, would interfere with evaluation of the investigational product or interpretation of subject safety or study results * Concurrent enrollment in another clinical study * Employees of the clinical study site or any other individuals involved with the conduct of the study, or immediate family members of such individuals * Exposure to an anti-IgE monoclonal antibodies (MAb) within 12 months prior to Screening * Positive drug screen at Screening or Day -1. A minimum list of drugs that will be screened for include amphetamines, barbiturates, cocaine, opiates, cannabinoids, and benzodiazepines * History of regular alcohol abuse within 12 months prior to Screening * History of sensitivity to any component of the investigational product formulation or a history of drug or other allergy that, in the opinion of the investigator or medical monitor, contraindicates their participation * Subjects with abnormal liver function test values (aspartate transaminase \[AST\] and alanine transaminase \[ALT\]) at Screening as defined as follows: a) Liver function test values \>= 1.5 times upper limit of normal (ULN) * Unwillingness or inability to follow the procedures outlined in the protocol * Positive test or history of hepatitis B or positive hepatitis C * Positive test or history of human immunodeficiency virus (HIV) or subject is known to be HIV seropositive * History of cancer, with the exception of basal cell carcinoma or in situ carcinoma of the cervix treated with apparent success * Women who are pregnant, breastfeeding, or lactating * Plans to donate blood during the study period * Hyper-IgE syndrome or bronchopulmonary aspergillosis * Prior history of Immune Complex Disease or type 3 hypersensitivity reactions to MAb administration * Known history of prior infusion reaction to MAb administration * History of untreated parasitic/helminthic infection within 6 months prior to Screening * Uses any of the following medications: a) Oral corticosteroids b) Medium to high dose Immunocorticosteroids (ICS)/ long-acting beta agonists (LABA) c) Immunosuppressives d) Beta blockers * If receiving allergy immunotherapy, must be on stable dose for 3 months. Must not receive allergy immunotherapy within 7 days of investigational product administration.