This is a Phase 1, randomized, placebo-controlled, multicenter study of CNTO 7160. The study consists of Screening Period, In-patient period (6 days for healthy participants, 11 days for asthmatic participants and atopic dermatitis participants) and outpatient period (105 days for healthy participants, 110 days for asthmatic and atopic dermatitis participants). The total duration of participation for each participant will be approximately 21 weeks for healthy participants, 25 weeks for asthmatic participants, and atopic dermatitis participants. All eligible participants will be randomly assigned to receive active agent or placebo. The study will be conducted in 2 parts. In Part 1, single ascending doses of CNTO 7160 or placebo will be administered to sequential cohorts of healthy participants as an IV infusion. In Part 2, ascending multiple doses of CNTO 7160 or placebo will be administered as IV infusions to sequential cohorts of participants with asthma or atopic dermatitis. Blood samples will be collected for assessment of pharmacokinetic and pharmacodynamics parameters in both part 1 and 2 parameters, along with assessment of safety and clinical effects in part 2. Participants' safety will be monitored throughout the study.